6312 A. SCHONBERG, M. ELKASCHEF, M. NOSSEIR AND M. ill. SIDKY VOl. 80

solute ethanol was hydrogenated over 3 mg. of 1Oyo palla- dium-on-carbon a t atmospheric pressure and room tem- perature. The measured volume of hydrogen consunled was 1.53 cc. (calcd. for 1 equivalent, 1.25 cc.). The cata- lyst was removed by centrifugation and washed with several portions of ether. Evaporation of the solvents yielded an depression. oil which partially crystallized when scratched with a glass stirring rod. The product was dissolved in 1 cc. of methanol and suffkient water added to make the solution cloudy. Cooling in an ice-bath with scratching caused crystallization

to occur. The crystalline acid was separated by centrifuga- tion and had m.p. 53-56’. Sublimation a t 75” (15 mm.) afforded 3.5 mg. (41.5%) of the pure acid, m.p. 55.5-57’ (reportedg 58”) . Mixed melting point comparison with ‘in authentic sample of XXII I ( I T I . ~ . 52-55.5*) exhibited no

The p-phenylphenacyl ester of X X I I I ITUS prepared a d found to melt a t 109-110° (reportedg 114”).

MADISOS 6, ~YIs.

[CONTRIBUTION FROM THE SATIOXAL RESEARCH CENTER AND THE CHEMISTRY DEP.4RTMES r, F,4CrLTU OF SCIENCE, CAIRO UNIVERSITY]

Experiments with 4-Thiopyrones and with 2,2’,6,6’-Tetrapheny14,4’-dipyrylene. The Piezochromism of Diflavylene

BY ALEXANDER SCHONBERG, MOHAXED ELKASCHEF, MICHAEL NOSSEIR AND XMIJIOUD MOHAMED SIDKY RECEIVED JUSE 2, 1958

~,(i-Uiaryl--l-pyrones are transformed into the corresponding 4-thiopyrones by using the thioacetic acid method. The action of mercuric chloride and of diazomethane (comp. I1 + 111) on these thioketones is described. Compound I I Ia is transformed by the action of lithium phenyl into 2,2’,6,6’-tetraphenyl-4,4’-dipj-rylene (XII ) , and 2,2‘-distyryl-dichromylene from 2-styryl-4-thiochromone (comp. IVb +. Vb -+ S‘Ib) is obtained by a similar process. The action of diphenyldiazo- methane (and of 9-diazofluorene) on 2,6-diphenyl-4-thiopyrone yields the ethylene derivatives X (yellow) and XI (red), respectively. The lack of reactivity of 2,2’,6,6’-tetra-phenyl-4,4’-dipyrylene is explained by the application of the resonance theory (comp. XI Ia +. XIIb ) . .A theory advanced to explain the piezochromic properties of diflavylene (’L’Ia) by reversible cis-trans changes (XIS‘a + XIVbl cannot be accepted as similar properties are also shown by S T ‘ and XVI.

Synthesis of 4-Thiopyrone from y-Pyrones by the Thionyl Chloride-Thioacetic Acid Method.- The transformation of ketones into the corre- sponding thioketones according to scheme X has been successfully carried out with benzophenones and xanthiones,‘ but not with y-pyrones. TVe have succeeded in obtaining 2, F-diphenyl-4-thio- pyrone (IIa) and 2,B-di-(p-methoxyphenyl)-d-thio- pyrone (IIb) according to the scheme

CHZCOSH

>C=S scheme A

?,Ci-Di-(p-methoxyphenyl)-4-pyrone (Ibj used in the synthesis of I Ib was prepared according to the method

IZCHBrCHBrCCHBrCHBrR __f

alc.

KOH

0

0 RC=CHCCH=CR

yellow color3 after a short time. n’ith 2,6-di-(p- methoxyphenyl)-4-thiopyrone (IIb) the color was orange. The color reaction probably is due to the formation of compounds of the type

1 r +S-HgC1 S-HgCl A* - K & K ~ c l -

P o O+

(b) Reactions with Diazomethane.-Nothing appears to be known about the action of diazo- methane on 4-thiopyrones. \Ye have found that the reaction with 2,6-diphenyl-4-thiopyrone (IIa) proceeds according to scheme B.

0

IIIa, R = CeH5

Compound IIa was obtained previously by Xrndt, et al.,2 by the action of phosphorus pentasulfide on Ia.

Reactions of 2,6-Diaryl-4-thiopyrones and 2- Styryl-4-thiochromones. (a) Color Reactions with Mercuric Chloride.-When mercuric chloride was added to a benzene solution of 2,6-diphenyl-4- thiopyrone (IIa), the colorless crystals acquired a

(1) A Schonberg. 0 Schutz and S h-ickel, B e y , 61, 1375 (1928) (2) I; Arndt, E Scholz and P Nachtwey, z b z d , 57, 1903 (1924)

Similar reactions have been observed previously with 4-thioflavone (IVa) 4 and were now observed with the 2-styryl-4-thiochromones IVb, c and VIIa,b respectively.

2-Styrylchromone (the oxygen analog of IVb) was recovered unchanged when treated with diazo- methane under the conditions leading to the for- mation of Vb and IVb.

(c) Reactions with Diphenyldiazomethane and Diazofluorene.-The action of diaryldiazornethane

(3) A. Schonberg, ibid., 58, 1793 (1923): comp. A. Schonberg in Houben-Weyl, “Methoden der Organischen Chemie,” Vol. 9, 1Y55, p p . 704-739.

(4) A. Schijnberg and S. Kickel, Ber., 64, 2323 (1931).

Dec. 5 , 1958 PIEZOCHROMISM OF DIFLAVYLENE 6313

L ” i z

VIIa, R = CH=CHC6Hs VIII b, R = CH=CHC6H,. OCH,(p) a, R = CH=CHC&

b, R = CH=CHCsH,OCH3(p)

on thioketones, e.g., thiobenzophenones, xanthiones and 4-thiochrom0nes,~ proceeds with the formation of ethylenesulfides, thermolabile compounds which form the corresponding ethylenes by losing sulfur. In some cases the ethylenes and not the ethylene sulfides were ~ b t a i n e d . ~

The action of diphenyldiazomethane on 2,6- diphenyl-4-thiopyrone (IIa) yields X via IX, and XI was obtained in the case of 9-diazofluorene; XI is red while X is yellow. The mother substance of X (the two phenyl groups attached to the ring in X replaced by hydrogen) is also yellow.6

CiH j-C,-CGH j CeH5-C-CsH6

Synthesis and Properties of 2,2’,6,6’-Tetra- phenyl-4,4’-dipyrylene (XI) .-When IIIa was treated with lithium phenyl, XI1 was obtained. Similarly the deep violet 2,2’-distyryldichromylene (VIb) was obtained from Vb. By a similar method dixanthylene (XIII) and diflavylene (VIa) were prepared previously. 2,2’,6,G’-Tetraphenyl4,4’-dipyrylene has been

obtained previously by a different method by Arndtf2 who drew attention to the great stability of this substance toward aqueous acids and alkalies which we confirmed. The substance is also very

(5) A. Schonberg, A. Fateen and M. Sammour, THIS JOURNAL, 78,

(6) H. Staudinger and S. Kon, A v n . , 384, 38 (1911). 1G89 (1956).

IIIa a c 0 H 5 x c 6 H 5

CiHs CH2S 0 4

CsH5

XI1 C,H5SLi

stable when treated with (a) potassium perman- ganate (in acetic acid as well as in pyridine), (b) hydrochloric acid and activated zinc, (c) sodium hydroxide, (d) sodium amalgam in the presence of amyl alcohol and (e) diazomethane. The chemo- stability of this substance cannot be explained by XI1 (which shows the formula of a vinyl ether), but by regarding the substance as a resonance hy- brid with strong contributions from structures characterized by separation of charges (compare inter alia XIIa - XIIb). The intense color of the substance as well as its thermostability are in accordance with this conception. Resonance XI1 - XIIa - XIIb should stabilize coplanarity of the two heterocyclic rings.

C d - h ~ c 6 H ~ c & x - C6H5

C6HS C s H s i / CsHs C6H5

- o +

XIIb o’+ XIIa

We regard 2,2’,6,6’-tetraphenyl-4,4’-dipyrylene as an analog of dixanthylene (XIII) (green form), the two heterocyclic rings being coplanar or nearly so, and we shall report on the importance of the chemistry of this dipyrylene derivative for the theory of thermochromism of XI11 in a later paper. g iii 6H5

CsH5 YH5 I Q 0

CsHs 0 / \ I \ o XI11 XIVa

XIVb Piezochromic Properties of Diflavylene (VIa) .-

Compound VIa (yellow crystals in the cold, yellow- orange a t room temperature which turn red on heating, forming a deep red melt) shows piezo- chromic properties : the crystals, when pressed in a mortar at room temperature, turn red.7 After some hours or days the red color is replaced by the original color; this change takes place within a few seconds when the crushed crystals are exposed to diethyl ether vapors.

According to Kortum,B et al., the piezochromism of VIa is due to the reversible formation of &-trans isomers (XIVa @ XIVb).

(7) A. Schonberg and W. Asker, J . Chrm. SOL., 272 (1942). (8) G. Kortum, W. Theilacker a n d G. Schreyer, Z. p h y s i k . Chen.,

Neuc Folge , 11, 182 (1957).

ti3 14

How ever 9- (p-nitrophenyl phenylmethylene) - xanthene9 (XV) and 10- (9'-xanthylene) -anthrone lo

(XVI) (these substances are related to VIa as they all iiiny be regarded as y-pyran derivatives) show piezochroinic properties similar to diflavylene. Here the formation of cis-trans isomers is iinpos- sible and we find it difficult to accept a theory which explains the piezochromic properties of VIa, but not of XV and XVII.

Experimental 2,6-Diphenyl-4-thiopyrone (IIa) .-2,6-Diphenyl-4-py-

ronc (1 g.) Tas refluxed with 15 g. of thionyl chloride for 5 hours, and the resulting solutioii was evaporated to dryness under reduced pressure. The residue was suspended in 311 ml. of dry benzeiie arid 2 nil. of tliioacetic acid and the mix- ture was refluxed for 5 hours in a carbon dioxide atmosphere. Removal of the solvent uitler reduced pressure gave a crystalline solitl which tvas recrystallized from ethyl alcohcil. Ked crystals of IIu (0.3 g.), idciiticai with a sample ob- tained from i',G-di]~lien~l-4-pyri~xic and phosphorus penta- sulfide2 (identification was carried out by m.p. and mixed 111.p.) were obtained. When these crystals nwe exposed to the ultraviolet light no striking change of color was ob- served, whereas 2,,(j-diphenyI-~-p?.rone gave an intense blue fluorescence.

2,6-Di-(p-methoxyphenylj-4-pyrone (Ib) .-To diaiiisal- acetone tetrabrriniitleil (28 g.) suspended in 228 inl. of boil- ing absolute alkyl alcohol a solution r i f 10 g. o f potassium liytircisitle i n absolute alcuhril was added portionn-ise. The reaction mixture mas refluxed (one hour), cooled anti liltcretl froin the deposited potassium bromide. The sol- X-ent was tlistillcti off under reduced pressure leaving an oil. I t was extracted with ether, the ether washed with water, tlrietl anti cvapiir:itetl leaving : i l l oil ( 1 3 g . 1 . X mixture of 15 g. of the oil and 1000 nil. of concentrated

hydrochloric acid (sp. gr. 1.19) was boiled for 6 hours under reflux. The criolcd acid solution containing the pyrone was tlecanted from the oil (A) and diluted with water. 2,6-Di- ip- i~ ie thox~-~l ienyl ) - l -p~~rc inc was precipitated. On re- pcatetlly boiling i;\) with h>-cirochloric acid small amounts of fairly pure Ib were obtained, total yield 1 g. The prod- uct was crystallized from benzene-petroleum ether (GO- 00') in yellliwish cr. 11s of n1.p. 189--l!iOo. I t dissolves in concentrated sulfuric aci(! giving a yellow color with stroiig green fluoresceiice, and alsii eyhibits green fluores- cence in the ultravicitet light; 11) is e d d y s o h b k in c d d methyl and ethyl alcohol.

AmZ. Calcii. for C19HIG04: C, 74.0; H, 5.2. Found: C, 73.7; €1, 3.2.

2,6-Di-(p-methoxyphenyl)-4-thiopyrone (IIb) . (1) Phos- phorus Pentasulfide Method.-To a solution of Ib (0.5 g.) in 25 nil. of dry benzene, 1.5 g. of pure phosphorus penta- sulfide was added and the reaction mixture was boiled under reflux for one holur then filtered hot. The residue w ~ i s washed with :I strong solution of ammonium sulfide theii atidcd to thc dark reddish-brown solid obtained upon evapo- ration of thc filtrate to dryness and the whole crop was crystallized from ethyl alcohol to give 0.15 g. o f I I b as reddish-brow1 crystals, 1n.p. 180'. It gives a yellow color with grcen fluoremmcc whet1 treated with concentrated sul- furic acid.

A n a l . Calcd. Lx Ci9111603S: C, 70.2; H, 4.9; S, 9.9. T ' l l u n r l : C , 70.1; F I , 5.1; s, 10.0.

-. ~- .

(Lij A. Schiintwr.;, 4. I:.itecii : r n d \ I . b:rtumour, l u x ~ J U I J R N A L , 79,

( I O ) A. SchOnLerg, A Ismnil and \T', Asker, J. Chem. SOL., 4 i 2

(11) 11. Yirl indcr and 15. Mumma, Btv., 36, 1170 (1903).

Gll9:' ( I 9 j 7 j

( 1 !M6)

(2) Thionyl Chloride Method.--2,6-Di-(p-nicthoxy- phenyl)-4-pyrone (0.2 g.) was refluxed with 5 g. of thionyl chloride for 5 hours, then the excess thionyl chloride was reinoved by distillaticin. The solid residue was suspended i n 10 ml. of dry benzene and 1 ml. of thioacctic acid was added. The reaction mixture was refluxeti in dry carboii dioxide :itmosphcre, then the solvent was distilled off under reduced pressure whereby crystals were obtained which were recrystallized from ethyl alcohol; IIb (0.12 g.) was ob- tained in reddish-brown crystals melting :it 178". I t gave a >-ellow cokir wit11 green fluorescence ~ l i e i i trcatcd witli concentrated sulfuric acid.

, - ln~! l . Caicd. for Cls i I l~OaS: S, <9.9. Fouiitl: S, 9.0. Action of Mercuric Chloride on IIa and 1Ib.-To thr rctl

solution of thc thiopyronc i n benzene a t room tciiipcrnturr cre adc!etl. Xfter sonic nie yellow in the case of

1Ia and oraiige in tlic ca while the solution was practically colorless in bot1

Action of Diazomethan 2,6-Diphenyl-4-thiopyrone (IIa).-'I'ii a soltitioil of I I a (1 g . ) in dry benzene (30 nil.) a n excess of diazoirietliaiie in d r y ether was added. The reaction inixti;rc was allowed t i l >t;inii for 1 days a t room teniperatiirc wi th a further : t r n i i u n t r i f di,tzoniethane solu- tion added each dav. T h e t1it:il vriluine of the solution was 2,W inl. containing (liazomcth.ine generated from 25 g. of nitrosornetli?-iurc~. . i i i i i l i i i o b t colorleas crystallinc solitl tlcposite!! which vias c(11l~te : i 11). tiltr~itii!:i and n-ashed with ether (0.5 g . ) , CIIiIip(!~iiiil I I Ia Lave a rel-brown colnr wit11 concentrated sulfuric acid arid the crystals were orange-ret1 wlieii vie\veri iii the ultra\-ioiet light. This substance in :I capillarj- tube when iininersed in a heating bath a t l~jl l ' b c - came rcd-lmiwi in ciilor within 30 seconds.

i t m i . Calcd. for Cs5H2s02S?: C, 77.3; If, 4.8; S, 11.7. Found: C, 77.2; 11, 5.1; S, 11.6.

Treatment of 2,6-Diphenyl-4-pyrone (Ia) with Diazometh- "The treatment of Ia with diazomethane in the same way as described under ~,C,-clipl1enyl-4-tlii~ip~-rc~ne led to the rccoverh- of the starting in,iterial (1r1.p. and mixed m.p. 1311")

Action of Diazomethane on: (a) 2-Styryl-4-thiochronione iIVb).-One gram of IVb'3 wa; treated with an ethereal .;lilation of diazornethane (fr~)in 6 g. of iiitrosomethy1iire:i~. Tlie reaction vessel wy:ts kept in tlie ice-chest overnight, theti lcft a t rooni tcmp iturc fw 2 tl:i>-s. The et!icre:tl s~~lutiriri which \vas red .li-brcin.ii in coliir I-iccaine pale I:i-~~wti ;itid pale yellow crystals sep:irntetl. The crystals iwrc crillected, washed with ether, arid crystallized froiii 1)eiizene-petrlileum ether (X-70°j ;is p d e yellow crystals o f 1%. 111.1). 180" dec., violet cdor with cnncentrated sulfuric :icitl; yield c a . 0.8 g.

.~iil,ii. C ~ l c d . for C15112a02S?: C, 77.3; 13, 1.8; S, 11.7. Found: C, 77.5: H, 4.6; 5, 11.8.

(b) 2-i4'-Methoxystyryl)-4-thiochromone ( IVc) .--Thc same procedure as with IT'b was follriwed. Uellow crystal.: i ; f I-(-, separated, crystallized from berizcne-yetri)lcuin ctllcr (50-70"i as ~-ellnwcrystals, 111.p. 176' dec.; violet ciliir witli ci,nccntrated sulfuric acid; yield co . 0.8 g .

. ln~oi. Calctl. for C3 i€h0&: C, 73.7; €1, 5.0; S. 1 O . G . Found: C, 73.8; H, 5 . 2 ; S, 10.4.

ic j 2-Styryl-4-thio-a-naphthopyrone (VIIa) .-One gr:ini ( i f \ - I Ia j was treated with an ethereal solution of t1i:tzoinetli- ane (from 6 g. of nitrijsonietlij-lurca), and left a t rooin twn- perature for 3 clays. The brown crystals of VIIa were tratii- formed into an arnorphous yellow substance which was collected and washed with ether. Compound VIIIa wvah crystallized from cliliirofori7i--petroleum ether (50-70",) a s ye l l~m~ crystals, 1ii.p. 188" dec. I t gave a violet color with concentruted sulfuric acid; yield ca. 0.7 g.

. - l f iu/ . Calcd. for C ~ ~ I I ~ O O S ~ : S, Found: S, I l ) . O . (d) 2-(4'-Methoxystyrylj-4-lhio-a-naphthopyrone (VIIb).

--The cxperimcrit XLS carried out its in the case of VIIx. hfter 2 days a second :irnount o f ethereal diazomethane solution (prepared from 4 g. vf nitrosomcthylurea) was added and tlie reaction mixture was left at room tempera- ture of 2 days. Pale yellow cryqtals of TTIIb separated, which were collected a l i i 1 crystallized from benzenc-pctrii-

(12) D. Vorlander and C .I. XIeyer, i 6 i d . , 45, 3355 (1912). ( 1 3 ) .4. SchSnberg, M. Sidky and C , .&Liz, T H r s JOURNAL, 7 6 , 3112

( 1 Y3-L) .

Dec. 3, 1958 PIEZOCHROMISM OF DIFLAVYLENE G31,5

leum ether (50-70"), m.p. 175" dec. It gave a deep violet color with concentrated sulfuric acid; yield ca. 0.7 g.

.4nczZ. Calcd. for C45H3404S2: C, 76.9; H, 4.8; S, 9.1. Found: C, 7 . 0 ; H, 5.3; S,9.2.

Action of Diphenyldiazomethane on 2,6-Diphenyl-4-thio- pyrone (IIa) .--A benzene solution of diphenyldiazomethane ( 2 g . ) was added to a solution of I I a (0.5 g.) in about 20 ml. of dry benzene at room tempcrature. The reaction mixture

The oily due, ~ h i c h remained after the removal of benzene under

reduced pressure, solidified on treatment with methyl alcohol to give yellow crystals of X (0.25 g.) , m.p. 193-194' (deep red melt); X produces a yellow greenish coloration with concen- trated sulfuric acid. Hardly any change of color was ob- served when a solution of this substance in dimethyl phthal- ate was heated. Compound X exhibited a green fluores- cence when exposed to the ultraviolet light.

Anal. Calcd. for C30H220: C, 90.4; H, 5 . 5 . Found: C, 90.3: H, 5.6.

Action of 9-Diazofluorene on 2,6-Diphenyl-4-thiopyrone (IIa).-To IIa (1 g.) 9-diazofluorene (1.2 g.) dissolved in 25 ml. of dry benzene xas added. The reaction mixture was refluxed for 5 hours and then allowed to stand overnight. The solvent was driven off under reduced pressure whereby :L crystalline solid was obtained, which on further crystalli- zation from benzene gave deep red crystals (0.4 g.), m.p. 265'; XI was red when viewed in ultraviolet light, and its dimethyl phthalate solution showed hardly any thermo- chromic change. It gives a red color with concd. sulfuric acid.

Anal. Calcd. for C~OHZOO: C, 90.9; H, 5.1. Found:

2,2 ',6,6'-Tetraphenyl-4,4'-dipyrylene (XII) .-Lithium phenyl mas prepared from 0.1 g. of lithium and 1 ml. of bromobenzene in 15 ml. of dry ether. Compound IIIa (0.5 9.) was added and the reaction mixture was refluxed for 4 hours and then left to stand overnight. The solid product which deposited was collected and crystallized from xylene to give XI1 (0.3 g . ) , m.p. and mixed m.p. 313°.2 The product gave the characteristic olive-green coloration with concentrated sulfuric acid.

Z,Z'-Distyrylene-dichromylene (VIb) .--1.2 g. of Vb was dissolved in 30 ml. of benzene (thiophene-free, dried over sodium) and treated with a solution of lithium phenyl (pre- pared from 1 g . of lithium and 9 g. of bromobenzene in about 50 ml. cf dry ether). The reaction mixture (deep violet) was refluxed gently for 2 hours in a nitrogen atmos- phere, then decomposed (ice-cold ammonium chloride anlution) . The solid substance obtained was crystallized from xylene as deep violet crystals of VIb, m.p. 285'. It gave a red-orange color with concentrated sulfuric acid; yield ca. 0.5 g.

Anal. Calcd. for C34H?402: C, 88.0; H, 5.1. Found: C, 88.2; H , 5.4.

Experiments Showing the Stability of 2,2',6,6'-Tetra- phenyl-4,4'-dipyrylene (XII) toward Various Chemical Agents.I4 (1) Potassium Permanganate. (a) In Acetic

left overnight and then refluxed for 3 hours.

c, 91.1; 13, 5.1.

A c i d . 4 . 4 g. of XI1 was partially dissolved in 8 ml. of boiling acetic acid. To the boiling solution 0.08 g. of potassium permanganate in 1 ml. of water was added during 8 minute? and the mixture was refluxed for 3 hours. The solution was then filtered while hot and the residue washed with water and dried at 100" (0.12 g.). The filtrate was allowed to cool and then diluted with water yielding crystals (0.25 g.).

(b) In Pyridine.-To XI1 (0.3 g.) dissolved in 30 nil. nf boiling pyridine (previously distilled over potassium per- manganate), a solution of 0.2 g. of potassium permanganate in 10 ml. of water was added and the mixture after being re- fluxed for 40 minutes was filtered while hot (filtrate -1). The residue was washed with dilute hydrochloric acid and then dried a t 100" (0.27 9.). Filtrate A was concentrated to dryness under diminished pressure and the solid residue treated with cold water. On standing colorless crystals (0.03 9.) of 2,6-diphenyl-4-pyrone were obtained (m.p. and mixed m.p. 140').

(2) Hydrochloric Acid. (a) In Alcohol.-A suspension of XI1 10.2 g . ) in ethanol (10 ml.) was treated with 2 .5 ml. of hydrochloric acid (sp. gr. 1.19) and the mixture was re- fluxed for 10 hours. The solvent was then distilled off under reduced pressure whereby the starting material was recovered.

(b) In Glacial Acetic Acid.--% mivture of 0.2 g. of XI1 and 10 ml. of hydrochloric acid (sp. gr. 1.19), was refluxed for 9 hours. The cold mixture yielded a solid which was crystallized from xylene (0.17 g.) .

(3) Hvdrochloric Acid and Zinc.-To a mixture of 20 ml. of glaciai acetic acid and 1 ml. of concentrated hydrochloric acid was added 2 g. of zinc powder (activated with copper sulfate). A vigorous evolution of gas took place and 0.2 g. of XI1 was added. After about 45 minutes the evolution of gas slowed down and the reaction mixture was refluxed for 5 minutes, cooled and filtered. A deep violet crystal- line product was obtained which was dried and extracted with xylene. From the xylene solution, 0.08 g. was ob- tained.

(4) Sodium Hydroxide.-To a solution of 0.3 g. of XI1 in 25 ml. of acetone, a solution of sodium hydroxide in 25 ml. of water was added, and the mixture was refluxed for 9 hours. After cooling, the solid was filtered off, washed with water and recrystallized from xylene (0.25 g.).

( 5 ) Sodium Amalgam.-To 0.5 g. of XI1 in amyl alcohol was added sodium amalgam (prepared from 0.5 g. of sodium and 34 g. of mercury). After 5 minutes reflux, the reaction mixture developed a red color and refluxing was continued for 3 hours. Upon filtration while hot, crystals were ob- tained which were recrystallized from xylene (0.4 g.) ,

( 6 ) Diazomethane.-To XI1 (0.25 g.) suspended in 65 ml. of dry benzene, 80 ml. of diazomethane in ether (pre- pared from 25 g. of nitrosomethylurea) was added in the cold. After 2 days a further amount of about 30 ml. of the same diazomethane solution was added. The reaction mixture was kept in the ice-chest for another 2 days and then filtered (0.2 g.) , The filtrate was brought to dryness and a further amount of the starting material was obtained (0.05 g.) . CAIRO, EGYPT

(11) I n the following experiments XI1 (recovered) was identified by the m.p. and the mixed m.p. test and by the color reaction (olive

green) with concentrated sulfuric acid, the grams in parentheses indi- cate t he yield.