Research Article Catalytic Synthesis of Pyrano- and...

Hindawi Publishing CorporationOrganic Chemistry InternationalVolume 2013 Article ID 693763 7 pageshttpdxdoiorg1011552013693763

Research ArticleCatalytic Synthesis of Pyrano- and Furoquinolines UsingNano Silica Chromic Acid at Room Temperature

Ali Gharib12 and Manouchehr Jahangir1

1 Department of Chemistry Islamic Azad University Mashhad Iran2 Agricultural Researches and Services Center Mashhad Iran

Correspondence should be addressed to Ali Gharib organiccatalyst2008gmailcom

Received 29 August 2012 Revised 2 October 2012 Accepted 16 April 2013

Academic Editor Chao Jun Li

Copyright copy 2013 A Gharib and M Jahangir This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Nano silica chromic acid (nano-SCA) is found to catalyze efficiently the three component-coupling reactions of aldehydes aminesand cyclic enol ethers such as 34-dihydro-2H-pyran and 23-dihydrofuran under mild conditions to afford the correspondingpyrano- and furanoquinolines in excellent yields with high endoselectivity Interestingly 23-dihydrofuran afforded selectivelyendoproducts under the similar reaction conditions Heterogeneous reaction conditions easy procedure short reaction time andhigh yields are some important advantages of this method

1 Introduction

Aza-Diels-Alder reactions rank among the most powerfulmethodologies for the construction of nitrogen-containingsix-membered ring compounds [1] The pyranoquinolinesand furanoquinolines are a class of nitrogen-containing het-erocycles which are synthesized by Aza-Diels-Alder method-ology Whereas pyranoquinolines exhibit biological proper-ties such as psychotropic antiallergic anti-inflammatory andestrogenic activities in addition to their use as pharmaceu-ticals [2 3] the furanoquinolines function as antagonistsof 5-hydroxytryptamine receptors in animals and have beenfound to be the most potent anti-inflammatory agents inaddition to being the most potent anti-inflammatory agents[4] The hetero-Diels-Alder reaction is becoming a mainstayfor heterocycle and natural product synthesis [5 6] Pyra-noquinoline derivatives are found to possess a wide spectrumof biological activities such as psychotropic antiallergenicanti-inflammatory and estrogenic activity [7]

Generally these compounds are prepared by Aza-Diels-Alder reactions of imines derived from aldehydes and amineswith dihydropyran or dihydrofuran Transition-metal com-plexes such as Co

2(CO)8 Ni(CO)

4[8 9] and InCl

3[8 9]

find their use for this reaction although BF3sdotOEt2has been

the most commonly used catalyst Thirteen various methods

[10] are reported in the literature which include the use ofGdCl3 ZrCl

4 LiClO

4 LiBF

4 I2 and montmorillonite clay to

promote this reaction Many Lewis acids cannot be utilizedfor the single-step coupling of aldehydes amines and enolethers because they will be decomposed or deactivated bythe amines and water formed in the intermediate imine-formation stepMost imines are hygroscopic unstable at hightemperature and difficult to purify so a one-pot three-com-ponent coupling protocol is highly desirable Nano silicachromic acid (nano-SCA) is a solid acid which can be usedfor different reactions either as reagent or as catalyst underheterogeneous conditions Collective nano-SCA would be asuperior proton source and is comparable with other solidacids such as nafion-H silica sulfuric acid and silica chloride[11ndash17] In this paper we wish to present a simple one-potprotocol for synthesis of pyrano[32-c]quinolines and furanoquinolines using nano-SCA benzaldehyde aniline and 34-dihydro-2H-pyran in THF as solvent and room temperatureconditions

2 Experimental

The chemicals used in the synthesis of all dyes were obtainedfrom Merck chemical company and were used without fur-ther purification The melting points were obtained using an

2 Organic Chemistry International

NH2

+ + +

R1 R2

R1

R1

R2

R2

O

O O

Nano SCATHF RT N

HNH

HHH

H

Nano silica chromic acid (Nano SCA)

CHO

4andashj 5andashj1 2 3a

Scheme 1 Synthesis of pyrano[32-c]quinolines using nano silica chromic acid (nano-SCA) catalyst

Nano-SiO2 OH + CrO2Cl2

OCrO2Cl + H2O

OCrO2Cl + HCl

Nano-SiO2

Nano-SiO2

Nano-SiO2 OCrO2OH + HCl

Scheme 2 Preparation of nano solid acid and HCl

Figure 1 Scanning Electron Microscope (SEM) image of nano-SCAresolution 15000X

Electrothermal IA 9100 Digital Melting Point apparatus 1Hand 13C NMR spectra were recorded on Bruker 400 ultra-shield NMR spectrometer (CDCl

3and acetone-119889

6) FT-IR

spectra were recorded on a magna-550 Nicolet GC-Massanalysis was performed on a GC-Mass model 5973 networkmass selective detector andGC6890 egilentmass spectra (GCsystem Hp-5 capillary 30m times 530 120583m times 15 120583m nominal) wereobtained with a Massens POEKTROMETER CH-7A VARINMAT BREMEN spectrometerThe Scanning ElectronMicro-scope (SEM) picture of nano-SCA is recorded with 15000XAll the yields were calculated from isolated products and GCwas used to establish their purities HPLC analysis employed

an internal standard method based on the absorbance of aproduct

21 Preparation of Nano Silica Chromic Acid A 500mL suc-tion flask equipped with a constant-pressure dropping funneland a gas inlet tube for conductingHCl gas over an adsorbingsolution (ie water) was used It was charged with nano silicagel (5 g) Then chromyl chloride (10 g) was added dropwiseover a period of 30min at room temperature HCl gas evolvedfrom the reaction vessel immediately After the addition wascomplete the mixture was shaken for 30min Nano silicachromic acid as a dark brown solid 12 g was obtained

22 General Procedure for the Synthesis of Pyrano- and Fura-noquinolines A mixture of aldehyde (1mmol) aryl amine(1mmol) and 34-dihydro-2H-pyran or 23-dihydrofuran(2mmol) in THF (10mL) nano silica chromic acid (nanoSCA) (007 g) was added and the mixture stirred at roomtemperature for an appropriate time After completion (fol-lowed by TLC) the solvent was removed under reduced pres-sure using a rotary evaporator The crude material was sub-jected to column chromatography over silica gel eluting withHexaneEtOAc (2ndash10) to afford the pure pyrano- or furo-quinolines

23 Selected Spectra

(4aS5S)-5-Phenyl-344a5610b-hexahydro-2H-pyrano[32-c]quinoline (4d) Mp 129-130∘C1H NMR (CDCl

3) 120575ppm

125ndash160 (m 3H) 180ndash190 (m 1H) 200ndash210 (m 1H) 375(dt 1H J = 115 25Hz) 400ndash410 (m 2H) 440 (d J = 25Hz1H) 475 (d J = 108Hz 1H) 650 (d J = 80Hz 1H) 670 (tJ = 75Hz 1H) 710 (t J = 75Hz 1H) 725 (d J = 80Hz 1H)

Organic Chemistry International 3

Table 1 Synthesis of pyrano- and furoquinolines using nano silica chromic acid (nano-SCA) catalyst in THF as solvent and at roomtemperature

Entry Product 4 Product 5 Time(min)

aYield ()bProduct ratio(trans cis)

4 5

1 HNH

O

HNH

O

55 89 85 15

2H

O

NHH

O

NH 70 93 80 20

3HN

H

O

F

HNH

O

F

95 91 90 10

4 HNH

O

HNH

O

65 94 90 10

5 HNH

O

O

HNH

O

O

70 90 85 15

6 HNH

O

F

HNH

O

F

86 915 87 13


Table 1 Continued



4 5

7HN

H

O

F

HNH

O

F

89 865 82 18

8 H

HO

O

NH

F

N+

Ominus

H

H

O

O

NH

F

N+

Ominus

100 88 79 21

9 HN

H

H

O

F

Cl

HN

H

H

O

F

Cl

120 875 78 22

aIsolated yields bIsomers were separated by column chromatography bRatio of the product was determined from the crude 1H NMR spectra

NH2

R1R1R1

CHO

R2

R2R2

O

OO

nano silica chromic acid (Nano SCA)

NH

HH

H

HNH

+ + +Nano SCATHF RT

3b 6bndashe 7bndashe

Scheme 3 Synthesis of furo[32-c]quinolines using nano silica chromic acid (nano-SCA) catalyst

740ndash755 (m 5H) 13CNMR (CDCl3) 120575ppm 223 244 393

550 692 745 1142 1174 1205 1277 1279 1285 12941309 1422 1445 IR (KBr cmminus1) 3325 2941 2864 16071482 1088 cmminus1 Calcd mass fractions of elements w forC18H19NO C 8148 H 722 N 528 Found C 8151 H 723

N 532 EIMSmz 265M+ 234 220 194 129 117 91 77

(4aR5S)-5-Phenyl-344a5610b-hexahydro-2H-pyrano[32-c]quinoline (5d) Mp 129-130∘C 1H NMR (CDCl

3) 120575ppm

125 (m 1H) 155ndash170 (m 3H) 210ndash220 (m 1H) 342 (dt1H J = 113 24Hz) 356 (dd 1H J = 113 24Hz) 380 (1HNH) 470 (d J = 27Hz 1H) 530 (d J = 56Hz 1H) 657 (dJ = 80Hz 1H) 676 (t J = 80Hz 1H) 704 (t J = 78Hz 1H)725ndash745 (m 6H) 13CNMR (CDCl

3) 120575ppm 181 257 390

594 607 728 1144 1180 1204 1269 1275 1277 12801284 1412 1452 IR (KBr cmminus1) 3340 2970 2850 16101490 1090 cmminus1 Calcd mass fractions of elements w forC18H19NO C 8148 H 720 N 528 Found C 8150 H

724 N 530 EIMSmz 265M+ 234 220 194 129 117 91 77

(3aRlowast4Rlowast9bRlowast)-4-(4-Bromophenyl)-233a459b-hexahy-drofuro[32-c]quinoline (6b)Mp 210ndash215∘C IR (neat cmminus1)3416 1617 1485 1353 1HNMR (CDCl

3) 120575ppm 753ndash742 (m

2H) 736ndash726 (m 3H) 703 (dt 1H J = 13 84Hz) 677 (t1H J = 75Hz) 652 (d 1H J = 79Hz) 52 (d 1H J = 77Hz)465 (d 1H J = 26Hz) 381ndash351 (m 1H) 275ndash265 (m 1H)223ndash207 (m 1H) 150 (m 1H) 13CNMR (CDCl

3) 120575ppm

285 494 584 685 846 845 1104 1193 1203 1266


Table 2 Synthesis of furoquinolines using nano silica chromic acid (nano-SCA) catalyst in THF as solvent and at room temperature


aYield ()bProduct ratio

6 7

1NH

O

BrH H

NH

O

BrH H

100 87 73 27

2NH

O

FCl

H H

NH

O

FCl

H H95 92 70 30

3O NH

O

ClH H

O

NHOCl

H H89 91 80 20

4HN

O

O

Cl H

H

minusON+

O

N

O

Cl

H

H

H

minusON+

120 885 75 15


Table 3 The effectiveness of varities solvents in the synthesis ofpyranoquinolines (Table 1 Entry 4 compounds 4a and 5a) usingnano silica chromic acid (nano-SCA) catalyst

Entry Solvent Time(min)

aYield()

bProduct ratio4a 5a

(transcis)1 THF 65 94 90 102 CCl4 91 725 81 193 CHCl3 74 69 80 204 CH2Cl2 69 73 73 275 DMF 115 68 65 356 DMSO 125 52 62 387 CH3CN 76 58 67 338 C6H5CH3 87 70 69 319 Free 95 59 62 2810 Pyridine 110 615 66 34aIsolated yield bIsomers were separated by column chromatographybRatio of the product was determined from the crude 1H NMR spectra

1285 1315 1395 1457 EIMSmz () 330 (M+) Calcd massfractions of elements w for C

17H16BrNO C 6182 H

486 N 422 Found C 6161 H 473 N 412

(3aRlowast4Slowast9bRlowast)-4-(4-Bromophenyl)-233a459b-hexahy-drofuro[32-c]quinoline (7b)Mp 142ndash147∘C IR (neat cmminus1)3417 1617 1352 1H NMR (CDCl

3) 120575ppm 751ndash746 (m 2H)

735ndash730 (m 3H) 708 (dt 1H J = 15 90Hz) 677 (t 1HJ = 75Hz) 657 (d 1H J = 75Hz) 453 (d 1H J = 52Hz)

403ndash395 (m 2H) 384ndash371 (m 2H) 242ndash230 (m 1H)206ndash193 (m 1H) 171ndash160 (m 1H) EIMS mz () 328(M+-1)13CNMR (CDCl

3) 120575ppm 287 496 582 687

844 1105 1197 1203 1257 1284 1289 1313 EIMS mz() 330 (M+) Calcd mass fractions of elements w forC17H16BrNO C 6182 H 485 N 422 Found C 6163 H

477 N 4161396 1457

3 Results and Discussion

A convenient rapid and one-pot method for the Aza-Diels-Alder reactions of aldimines with dihydropyran or dihydro-furan to afford the corresponding pyrano and furo[32-c]quinolines in high yields with high diastereoselectivity in ashort period of time has been developed We now report ourobservations on the synthesis of pyrano- and furoquinolinesby a one-pot three-component coupling of anilines (1) ben-zaldehydes (2) and 34-dihydro-2H-pyran or 23-dihydro-furan (3a b) catalyzed by nano silica chromic acid (nano-SCA) at room temperature (Scheme 1)

Nano-SCA is formed via the reaction between nano silicagel (mesh 20 nm) and chromyl chloride CrO

2Cl2 Then HCl

and SiO2-CrO3H are formed in situ by the reaction between

nano-SCA and H2O in wet SiO

2(Scheme 2)

The Scanning Electron Microscope (SEM) picture ofnano-SCA is recorded with 15000X (Figure 1)

In a typical procedure benzaldehyde and aniline werereacted with 34-dihydro-2H-pyran in the presence of nanosilica chromic acid (nano-SCA) catalyst in THF at room tem-perature To our surprise the reaction yielded the corre-sponding pyrano[32-c]quinoline within 65min as a mixture


Table 4The effectiveness of temperature in the synthesis of pyrano-quinolines (Table 1 Entry 4 compounds 4a and 5a) in THF assolvent

Entry Catalyst Temp(∘C)

aYield()

Time(min)

bProduct ratio4a 5a

(trans cis)1 Nano SCA 25 94 65 90 102 Nano SCA Reflux 975 52 92 83 ZnO Reflux 645 91 68 324 ZnO 25 605 109 61 395 H2SO4 Reflux 86 88 84 266 H2SO4 25 80 99 79 217 Bi(OTf)3 Reflux 795 92 71 398 Yb(OTf)3 Reflux 845 96 66 349 Free Reflux 43 116 58 4210 Free 25 36 168 49 51aIsolated yield bIsomers were separated by column chromatographybRatio of the product was determined from the crude 1H NMR spectra

of cis- and trans-isomers in the ratio of 10 90 in an overallyield of 94 Easy separation of the isomers was achievedby chromatography over silica gel (Scheme 1) We could es-tablish the structures of these isomers based on 1H NMRdata and the IR spectrum is especially strong differentiatingisomers of diverse functional groups being the spectroscopyof choice for instant classification of molecules And the ratioof the isomers obtained in each reaction was determinedfrom the 1HNMR spectrum of the crude product and thestructures of the products were characterized on the basis ofspectroscopic (IR 1H NMR 13C NMR and GC-MS) dataof the pure compounds from column chromatography(Scheme 1 compounds 4andashj and 5andashj) All the reactionsinvolving various aldehydes containing electron donatingand electron withdrawing substituents formed imine insitu and in all cases the imines generated from aromaticaldehydes and anilines reacted with dihydropyran and thethree-component one-pot reaction proceeded to give the cor-responding pyranoquinolines in high yields and with highdiastereoselectivity The results are listed in Table 1

The reaction proceeded in a short period of time and af-forded the corresponding furo[32-c]quinolines a mixture ofcis- and trans-isomers (Scheme 3 compounds 6 and 7) whichcould be separated and purified by column chromatographyover silica gel to give a solid that was defined by GC-MS IRand 1HNMR (Scheme 3) and the results are listed in Table 2

Several aldimines (formed in situ from aromatic aldehy-des and anilines in THF) reacted smoothly with 23-dihy-drofuran using nano silica chromic acid (nano-SCA) cata-lyst to afford the corresponding furano[32-c]quinolines ascistrans mixtures in 87ndash92 yield (Scheme 3 and Table 2)Also the structures of the products were established on thebasis of spectroscopic (IR 1HNMR 13CNMR and GC-MS)data of the pure compounds (Scheme 3 compounds 6 and 7)

To further optimize the reaction condition in terms of sol-vent we tried the reaction in various solvents and also with-out solvent It was noticed that THF as solvent appears to be

Table 5 The effectiveness of varities catalysts in the synthesis ofpyranoquinolines (Table 1 Entry 4 compounds 4a and 5a) in THFas solvent

Entry CatalystaYield()

Time(min)

bProduct ratio4a 5a

(trans cis)1 Nano SCA 94 65 90 102 ZnO 61 91 64 363 H2SO4 815 88 80 204 Bi(OTf)3 77 92 66 345 Yb(OTf)3 78 96 61 396 Free 365 145 53 47aIsolated yield bIsomers were separated by column chromatographybRatio of the product was determined from the crude 1H NMR spectra

superior in improving the trans selectivity of the product(Table 1 Entry 5) The results are summarized in Table 3 andthe major isomer is 4a (trans-isomer) [16 17]

When the experiment was conducted at room tempera-ture a good and convenient amount of the correspondingproduct was generated (Table 4 Entry 1 and Tables 1 and2) Upon heating (reflux conditions) however the reactionwas greatly accelerated (Table 4 Entries 2 3 5 and 7ndash9) andwith higher yield (Table 4 Entry 2) The major isomer oftendepends on the reaction temperature Higher temperaturegave more of the thermodynamically stable trans-isomerproducts while lower temperatures resulted in fast formationof the kinetically favored cis-isomer products (94 yield)(Table 4 Entry 1) A moderate yield (975) was obtainedaccompanied by high trans selectivity of the product 92 8(Table 4 Entry 2)

Initially we compared the catalytic performance ofH2SO4 Yb(OTf)

3 Bi(OTf)

3 ZnO and nano silica chromic

acid (nano-SCA) catalyst in the synthesis of pyrano- andfuroquinolines The results are shown in Table 5 The yield ofproduct decreases in the following order

(Nano SCA) gt H2SO4gt Yb(OTf)

3

gt Bi(OTf)3gt ZnO

(1)

As could be seen nano silica chromic acid catalyst ismore effective than the other catalysts and in the presence ofthis catalyst the highest yields of products are obtained Theresults (Table 4) show that nano silica chromic acid catalystis better with respect to yield and to reaction In all casesthe nano silica chromic acid catalyst shows higher activitycompared with other catalysts ZnO Bi(OTf)

3 Yb(OTf)

3

and H2SO4(Table 5 Entries 2ndash5) Nano silica chromic acid

(nano-SCA) catalyst shows a higher selectivity and this cat-alyst is an efficient solid acid catalyst for highly selective syn-thesis of pyrano- and furoquinolines

4 Conclusion

Nano-SCA is noncorrosive and safe solid acid with easy sep-aration and recovery from reaction mixture We have syn-thesized azo pyrano- and furoquinolines using nano silica


chromic acid as a solid acid at room temperature and in goodyields under mild reaction conditions with high diastereos-electivity The yields of products were good to excellent andthe reaction times were very suitable This paper describes anovel and efficient method for the synthesis of pyrano- andfuranoquinolines using nano-SCA as promoters

References

[1] S M Weinreb ldquoHeterodienophile additions to dienesrdquo inComprehensive Organic Synthesis B M Trost I Fleming andL A Paquette Eds vol 5 p 401 Pergamon Press Oxford UK1991

[2] R W Carling P D Leeson A M Moseley et al ldquo2-Car-boxytetrahydroquinolines Conformational and stereochemicalrequirements for antagonism of the glycine site on the NMDAreceptorrdquo Journal of Medicinal Chemistry vol 35 no 11 pp1942ndash1953 1992

[3] MRamesh P SMohan andP Shanmugam ldquoA convenient syn-thesis of flindersine atanine and their analoguesrdquo Tetrahedronvol 40 no 20 pp 4041ndash4049 1984

[4] J Sharada Y R Kumari and M Kanakalingeswara Rao ldquoSyn-thesis and biological activity of furoquinolines 2-aroyl-4-meth-yl46-dimethyl-3-phenyl-furo [32-c] quinolinesrdquo Indian Jour-nal of Pharmaceutical Sciences vol 49 no 1 pp 17ndash21 1987

[5] D L Boger and S M WeinrebHetero Diels-Alder Methodologyin Organic Synthesis Chapters 2 and 9 Academic San DiegoCalif USA 1987

[6] P Buonora J C Olsen and T Oh ldquoRecent developments in im-ino Diels-Alder reactionsrdquo Tetrahedron vol 57 pp 6099ndash61382001

[7] J V Johnson B S Rauckman D P Baccanari and B Rothldquo24-diamino-5-benzylpyrimidines and analogues as antibacte-rial agents 12 12-dihydroquinolylmethyl analogues with highactivity and specificity for bacterial dihydrofolate reductaserdquoJournal of Medicinal Chemistry vol 32 no 8 pp 1942ndash19491989

[8] R Annunziata M Cinquini F Cozzi V Molteni and OSchupp ldquoA new multicomponent synthesis of 1234-tetrahy-droquinolinesrdquoTetrahedron vol 53 no 28 pp 9715ndash9726 1997

[9] G Babu andP T Perumal ldquoConvenient synthesis of pyrano[32-c]quinolines and indeno[21- c]quinolines by iminoDiels-Alderreactionsrdquo Tetrahedron Letters vol 39 no 20 pp 3225ndash32281998

[10] L S Povarov ldquo120572120573-unsaturated ethers and their analogues inreactions of diene synthesisrdquo Russian Chemical Reviews vol 36no 9 p 656 1967

[11] M A Zolfigol ldquoSilica sulfuric acidNaNO2as a novel heteroge-

neous system for production of thionitrites and disulfides undermild conditionsrdquo Tetrahedron vol 57 no 46 pp 9509ndash95112001

[12] M A Zolfigol B F Mirjalili A Bamoniri et al ldquoNitration ofaromatic compounds on silica sulfuric acidrdquo Bulletin of the Ko-rean Chemical Society vol 25 no 9 pp 1414ndash1416 2004

[13] M A Zolfigol M Bagherzadeh S Mallakpour et al ldquoMildand heterogeneous oxidation of urazoles to their correspondingtriazolinediones via in situ generation Cl+ using silica sulfuricacidKClO

3or silica chlorideoxone systemrdquo Catalysis Commu-

nications vol 8 no 3 pp 256ndash260 2007[14] M A Zolfigol R Ghorbani-Vaghei S Mallakpour G Che-

hardoli A G Choghamarani and A H Yazdi ldquoSimple con-venient and heterogeneous method for conversion of urazoles

to triazolinediones using NNN1015840N1015840-tetrabromobenzene-13-disulfonylamide or trichloromelamine under mild and hetero-geneous conditionsrdquo Synthesis no 10 pp 1631ndash1634 2006

[15] A R Hajipour A Zarei L Khazdooz S A Pourmousavi andA E Ruoho ldquoSilicasulfuric acidNaNO

2as a new reagent for

deprotection of SS-acetals under solvent-free conditionsrdquo Bul-letin of the Korean Chemical Society vol 26 no 5 pp 808ndash8102005

[16] E Boanini P Torricelli M Gazzano R Giardino and A BigildquoNanocomposites of hydroxyapatite with aspartic acid and glu-tamic acid and their interaction with osteoblast-like cellsrdquo Bio-materials vol 27 no 25 pp 4428ndash4433 2006

[17] G Sabitha M S K Reddy K Arundhathi and J S YadavldquoVCl3-Catalyzed aza-Diels-Alder reaction one-pot synthesisof pyrano[32-c]quinolines and furo[32-c]quinolinesrdquo Arkivocvol 2006 no 6 pp 153ndash160 2006

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Organic Chemistry International

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CatalystsJournal of


NH2

+ + +

R1 R2

R1

R1

R2

R2

O

O O

Nano SCATHF RT N

HNH

HHH

H

Nano silica chromic acid (Nano SCA)

CHO

4andashj 5andashj1 2 3a

Scheme 1 Synthesis of pyrano[32-c]quinolines using nano silica chromic acid (nano-SCA) catalyst

Nano-SiO2 OH + CrO2Cl2

OCrO2Cl + H2O

OCrO2Cl + HCl

Nano-SiO2

Nano-SiO2

Nano-SiO2 OCrO2OH + HCl

Scheme 2 Preparation of nano solid acid and HCl

Figure 1 Scanning Electron Microscope (SEM) image of nano-SCAresolution 15000X

Electrothermal IA 9100 Digital Melting Point apparatus 1Hand 13C NMR spectra were recorded on Bruker 400 ultra-shield NMR spectrometer (CDCl

3and acetone-119889

6) FT-IR

spectra were recorded on a magna-550 Nicolet GC-Massanalysis was performed on a GC-Mass model 5973 networkmass selective detector andGC6890 egilentmass spectra (GCsystem Hp-5 capillary 30m times 530 120583m times 15 120583m nominal) wereobtained with a Massens POEKTROMETER CH-7A VARINMAT BREMEN spectrometerThe Scanning ElectronMicro-scope (SEM) picture of nano-SCA is recorded with 15000XAll the yields were calculated from isolated products and GCwas used to establish their purities HPLC analysis employed

an internal standard method based on the absorbance of aproduct

21 Preparation of Nano Silica Chromic Acid A 500mL suc-tion flask equipped with a constant-pressure dropping funneland a gas inlet tube for conductingHCl gas over an adsorbingsolution (ie water) was used It was charged with nano silicagel (5 g) Then chromyl chloride (10 g) was added dropwiseover a period of 30min at room temperature HCl gas evolvedfrom the reaction vessel immediately After the addition wascomplete the mixture was shaken for 30min Nano silicachromic acid as a dark brown solid 12 g was obtained

22 General Procedure for the Synthesis of Pyrano- and Fura-noquinolines A mixture of aldehyde (1mmol) aryl amine(1mmol) and 34-dihydro-2H-pyran or 23-dihydrofuran(2mmol) in THF (10mL) nano silica chromic acid (nanoSCA) (007 g) was added and the mixture stirred at roomtemperature for an appropriate time After completion (fol-lowed by TLC) the solvent was removed under reduced pres-sure using a rotary evaporator The crude material was sub-jected to column chromatography over silica gel eluting withHexaneEtOAc (2ndash10) to afford the pure pyrano- or furo-quinolines

23 Selected Spectra

(4aS5S)-5-Phenyl-344a5610b-hexahydro-2H-pyrano[32-c]quinoline (4d) Mp 129-130∘C1H NMR (CDCl

3) 120575ppm

125ndash160 (m 3H) 180ndash190 (m 1H) 200ndash210 (m 1H) 375(dt 1H J = 115 25Hz) 400ndash410 (m 2H) 440 (d J = 25Hz1H) 475 (d J = 108Hz 1H) 650 (d J = 80Hz 1H) 670 (tJ = 75Hz 1H) 710 (t J = 75Hz 1H) 725 (d J = 80Hz 1H)





4 5

1 HNH

O

HNH

O

55 89 85 15

2H

O

NHH

O

NH 70 93 80 20

3HN

H

O

F

HNH

O

F

95 91 90 10

4 HNH

O

HNH

O

65 94 90 10

5 HNH

O

O

HNH

O

O

70 90 85 15

6 HNH

O

F

HNH

O

F

86 915 87 13


Table 1 Continued



4 5

7HN

H

O

F

HNH

O

F

89 865 82 18

8 H

HO

O

NH

F

N+

Ominus

H

H

O

O

NH

F

N+

Ominus

100 88 79 21

9 HN

H

H

O

F

Cl

HN

H

H

O

F

Cl

120 875 78 22


NH2

R1R1R1

CHO

R2

R2R2

O

OO


NH

HH

H

HNH

+ + +Nano SCATHF RT





N 532 EIMSmz 265M+ 234 220 194 129 117 91 77


3) 120575ppm


3) 120575ppm 181 257 390


724 N 530 EIMSmz 265M+ 234 220 194 129 117 91 77


3) 120575ppm 753ndash742 (m


3) 120575ppm

285 494 584 685 846 845 1104 1193 1203 1266





6 7

1NH

O

BrH H

NH

O

BrH H

100 87 73 27

2NH

O

FCl

H H

NH

O

FCl

H H95 92 70 30

3O NH

O

ClH H

O

NHOCl

H H89 91 80 20

4HN

O

O

Cl H

H

minusON+

O

N

O

Cl

H

H

H

minusON+

120 885 75 15




aYield()

bProduct ratio4a 5a



17H16BrNO C 6182 H

486 N 422 Found C 6161 H 473 N 412


3) 120575ppm 751ndash746 (m 2H)



3) 120575ppm 287 496 582 687


477 N 4161396 1457




2Cl2 Then HCl



2(Scheme 2)






aYield()

Time(min)

bProduct ratio4a 5a








Time(min)

bProduct ratio4a 5a





3 Bi(OTf)




3

gt Bi(OTf)3gt ZnO

(1)


3 Yb(OTf)

3



4 Conclusion




References

































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





4 5

1 HNH

O

HNH

O

55 89 85 15

2H

O

NHH

O

NH 70 93 80 20

3HN

H

O

F

HNH

O

F

95 91 90 10

4 HNH

O

HNH

O

65 94 90 10

5 HNH

O

O

HNH

O

O

70 90 85 15

6 HNH

O

F

HNH

O

F

86 915 87 13


Table 1 Continued



4 5

7HN

H

O

F

HNH

O

F

89 865 82 18

8 H

HO

O

NH

F

N+

Ominus

H

H

O

O

NH

F

N+

Ominus

100 88 79 21

9 HN

H

H

O

F

Cl

HN

H

H

O

F

Cl

120 875 78 22


NH2

R1R1R1

CHO

R2

R2R2

O

OO


NH

HH

H

HNH

+ + +Nano SCATHF RT





N 532 EIMSmz 265M+ 234 220 194 129 117 91 77


3) 120575ppm


3) 120575ppm 181 257 390


724 N 530 EIMSmz 265M+ 234 220 194 129 117 91 77


3) 120575ppm 753ndash742 (m


3) 120575ppm

285 494 584 685 846 845 1104 1193 1203 1266





6 7

1NH

O

BrH H

NH

O

BrH H

100 87 73 27

2NH

O

FCl

H H

NH

O

FCl

H H95 92 70 30

3O NH

O

ClH H

O

NHOCl

H H89 91 80 20

4HN

O

O

Cl H

H

minusON+

O

N

O

Cl

H

H

H

minusON+

120 885 75 15




aYield()

bProduct ratio4a 5a



17H16BrNO C 6182 H

486 N 422 Found C 6161 H 473 N 412


3) 120575ppm 751ndash746 (m 2H)



3) 120575ppm 287 496 582 687


477 N 4161396 1457




2Cl2 Then HCl



2(Scheme 2)






aYield()

Time(min)

bProduct ratio4a 5a








Time(min)

bProduct ratio4a 5a





3 Bi(OTf)




3

gt Bi(OTf)3gt ZnO

(1)


3 Yb(OTf)

3



4 Conclusion




References

































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Table 1 Continued



4 5

7HN

H

O

F

HNH

O

F

89 865 82 18

8 H

HO

O

NH

F

N+

Ominus

H

H

O

O

NH

F

N+

Ominus

100 88 79 21

9 HN

H

H

O

F

Cl

HN

H

H

O

F

Cl

120 875 78 22


NH2

R1R1R1

CHO

R2

R2R2

O

OO


NH

HH

H

HNH

+ + +Nano SCATHF RT





N 532 EIMSmz 265M+ 234 220 194 129 117 91 77


3) 120575ppm


3) 120575ppm 181 257 390


724 N 530 EIMSmz 265M+ 234 220 194 129 117 91 77


3) 120575ppm 753ndash742 (m


3) 120575ppm

285 494 584 685 846 845 1104 1193 1203 1266





6 7

1NH

O

BrH H

NH

O

BrH H

100 87 73 27

2NH

O

FCl

H H

NH

O

FCl

H H95 92 70 30

3O NH

O

ClH H

O

NHOCl

H H89 91 80 20

4HN

O

O

Cl H

H

minusON+

O

N

O

Cl

H

H

H

minusON+

120 885 75 15




aYield()

bProduct ratio4a 5a



17H16BrNO C 6182 H

486 N 422 Found C 6161 H 473 N 412


3) 120575ppm 751ndash746 (m 2H)



3) 120575ppm 287 496 582 687


477 N 4161396 1457




2Cl2 Then HCl



2(Scheme 2)






aYield()

Time(min)

bProduct ratio4a 5a








Time(min)

bProduct ratio4a 5a





3 Bi(OTf)




3

gt Bi(OTf)3gt ZnO

(1)


3 Yb(OTf)

3



4 Conclusion




References

































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





6 7

1NH

O

BrH H

NH

O

BrH H

100 87 73 27

2NH

O

FCl

H H

NH

O

FCl

H H95 92 70 30

3O NH

O

ClH H

O

NHOCl

H H89 91 80 20

4HN

O

O

Cl H

H

minusON+

O

N

O

Cl

H

H

H

minusON+

120 885 75 15




aYield()

bProduct ratio4a 5a



17H16BrNO C 6182 H

486 N 422 Found C 6161 H 473 N 412


3) 120575ppm 751ndash746 (m 2H)



3) 120575ppm 287 496 582 687


477 N 4161396 1457




2Cl2 Then HCl



2(Scheme 2)






aYield()

Time(min)

bProduct ratio4a 5a








Time(min)

bProduct ratio4a 5a





3 Bi(OTf)




3

gt Bi(OTf)3gt ZnO

(1)


3 Yb(OTf)

3



4 Conclusion




References

































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




aYield()

Time(min)

bProduct ratio4a 5a








Time(min)

bProduct ratio4a 5a





3 Bi(OTf)




3

gt Bi(OTf)3gt ZnO

(1)


3 Yb(OTf)

3



4 Conclusion




References

































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



References

































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Research Article Catalytic Synthesis of Pyrano- and...

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