PYRROLE Occurs in coal tar. Colourless liquid with odour of chloroform, mp -24C, bp 131C, slightly...
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Transcript of PYRROLE Occurs in coal tar. Colourless liquid with odour of chloroform, mp -24C, bp 131C, slightly...
PYRROLE
• Occurs in coal tar. Colourless liquid with odour of chloroform, mp -24C, bp 131C, slightly soluble in water. It has resonance energy of 100KJ per mole. It is found in proline and nicotine.
RETROSYNTHESIS OF PYRROLE
NNOH
NH2O
OH2
NH2
H
O
X
OH2
-NH3
O O
OH2
N
OH
N
OH
OH
NH2
OH
O
NH2
O
O
+
+
Acid-base rxns of pyrrole
• Protonation occurs at C-2
N N
N
NaH
NNa
N
BuLi
NLi
+ H+
+
POLYMERS
protonation on C2
+
+
_
+
• Electrophilic substitution rxns
NH
SO2Cl
NH
Cl
NH
Br2/acetic anhydrideNH
Br
+ heat
+
2
NH
HNO3/acet anhNH
NO2
NH
NH
SO3HSO3/pyri
+
+100C
NH
NH
O O
H2O2
NH
H2/NiNH
OXIDATION
REDUCTION
or high pressure
high temp
• COMPOUNDS CONTAINING PYRROLE OR PYRR• OLIDINE
NH
CO2HN
N
CH3
PROLINE NICOTINE
• IMIDAZOLEN
N
N
N N
N
4H-IMIDAZOLE
WEAKER BASE THAN PYRROLE DUE TO ADDITIONAL N
SUBST OCCURS AT POSITIONS 4,5
+ HCl +
RETROSYNTHESIS OF IMIDAZOLE
N
NH
N
NHOH
H
N
NHOH
H
OH
OH2
-NH3
NH
OO
NH3
H O2
+
N
NH
N
NHOH
H
O
X NH
NH2
H O2
+
• COMPOUNDS CONTAINING IMIDAZOLE
NH
NNH2
HO2C
NH
NNH2
HISTIDINE HISTAMINE
Vasodilator, high level causes allergic rxnssuppressed by anti-histamines-blocks allegy causing H-receptors
PYRAZOLE CONT’D
N
N
2H-PYRAZOLE
subst occurs at C-4Elec
analgesic, anti-inflammatory
PYRAZOLE
This is a weaker base than imidazole
PYRAZOLE CONT’D
N
NOH2
NH
NHOH
OH2
NH
NHOH
OH
O
O
NH2NH2
+
RETROSYNTHESIS OF OXAZOLE
N
O
OH2N
OOH
N
OHO
NH
OO
OXAZOLE CONT’D
NH
OO
NH2
OO
X
X
OO
NH2
OR
A
BA
B
OXAZOLE CONT’D
• OXAZOLE IS COLOURLESS LIQ, SMELLS LIKE PYRIDINE, SOL, IN WATER, ARYL-SUBSTITUTED STRONGLY FLUORESCENT. SUITABLE AS LUMINOUS SUBSTANCES (LIQ SCINTILLATION COUNTERS OR USED AS BRIGHTENING AGENTS)
SUMMARY-RXNS
O NH
S
O
N
N
N
S
NE EE
N N
EE E
1,3-benzoxazole
• Colourless liq, sol. In water. Aroma constituent in cocoa, coconuts, walnuts and beer. Derivative occurs in fireflies.
S
N
Benzothiazole or 1,3-benzothiazole
• Colourless crystals, moderately sol in water, very soluble in ethanol
NH
N
Benzoimidazole
BENZO[b]THIPHENE
• Benzo[b]thiophene occurs in coal tar and roasted coffee beans
S
Benzo[b]thiophene
• Derivative used as antibacterial drug(with nitrophenyl side chain), colourless, oily liq, water insoluble, occurs in coal tar
O
Benzo[b]furan or 1-benzofuran
O
Isobenzo[b]furan or 2-benzofuran
• Colourless, fluorescent crystals,occurs in coal tar
O
Dibenzo[b,d]furan
• Electro subs occurs at C-3. Colourless solid leaflet crystals, mod. Sol in water. Occurs in coal tar and jasmine oil
NH
benzo[b]pyrrole or
1H-indole
• Bufotein-poison on frog skin; psilocin-causes hallucinations
NH
OHN(CH3)2
NH
N(CH3)2
OH
bufotein
psilocin
NOMENCLATURE SIX MEMB.
O O
2H-PYRAN 4H-PYRAN
NO
N
O
6H-1,2-OXAZINE 2H-1,3-OXAZINE
N N
PYRIDINE 3,4-DIHYDROPYRIDINE
NN
N
N
PYRIDAZINEPYRIMIDINE
N N
QUINOLINE ISOQUINOLINE
Si Sisiline silinane
P P
PHOSPHININE PHOSPHINANE
PYRILIUM ION
• Planar and slightly distorted hexagon. It is aromatic. Positive charge at 2,4,6.Hence nucleophilic attack at 2,4,6
O+
RING OPENING
• OH adds at pos 2 and with heating ring opens
O OOHOH O
+ +
OH-
• Ring opens to form 1,5-diketone or 1,5-dialdehyde
O O
RING OPENING CON’D
• Grignard reagent can also add at pos 2. Heating opens up the ring to form dienone
O O R O RRMgX
+
2H-PYRAN
• The parent compd has not yet been isolated. However, 2,2-disubstituted derivatives have been isolated
O Oparent
disubstituted derivative
THERMAL RING OPENING OF 2H-PYRAN DERIVATIVE
• This compd undergoes thermal ring opening
O Oheat
2H-PYRAN-2-ONE
• Bp of 208C, colourless liq. It behaves like 1,3-dienes and also like lactones
O O
2H-PYRAN-2-ONE
RXN OF 2H-PYRAN-2-ONE
O O
RMgX
O
2H-PYRAN-2-ONE
SYNTHESIS OF TETRAHYDROPYRAN
• Dehydration rxn catalyzed by acid. Loss of water with subsequent cyclization
OHOH O
heat
2H-CHROMENE
• It is found in natural products like plants
O
2H-CHROMENE
OR 2H-1-BENZOPYRAN
2H-CHROMEN-2-ONE or coumarin
• Occurs in plants (lavender), mp 68C, colourless crystalline solid. Reacts like lactone.
O O
2H-CHROMENE-2-ONE
OR 2H-1-BENZOPYRAN-2-ONE
OR COUMARIN
LACTONE RING OPENING
• Ring opens to form free carboxylic acid
O O
OH
CO2HO -
1-BENZOPYRILIUM ION
• The derivative of this compd is found in leaves and flowers. It gives various colours to leaves and flowers
O+
BENZOPYRILIUM ION CONT’D
• Numerous red, blue and violet pigments of blossom and leaves are made of this derivative. Occurs as glycosides(anthocyanins)
O
OH
OH
OH
+
4H-PYRAN
• Unlike 2H-Pyran, the parent compd is known. It is synthesized from 1,5-diketone or 1,5-dialdehyde
O4H-PYRAN
SYNTHESIS OF 4H-PYRAN
O O O
_ H O2
heat
4H-PYRAN-4-ONE
• Mp 32C, colourless, crystalline. Occurs in the bark of larch tree; also formed by dry distillation of starch and cellulose. Also found in opium
O
O
4H-PYRAN-4-ONE
4H-1-BENZOPYRAN(4H-CHROMENE)
• Derivatives found in plants
O
4H-1-BENZOPYRAN
4H-CHROMENEOR
4H-CHROMEN-4-ONE(4H-1-BENZOPYRAN-4-ONE)
• Mp 59C, colourless needles. Also known as chromone. Derivative found in plants
O
O
4H-1-BENZOPYRAN-4-ONE
4H-CHROMENE-4-ONEOR
OTHER DERIVATIVES OF 4H-CHROMEN-4-ONE
• Phenyl at pos 2 gives FLAVONES, eg apigenin, leteolin. Occurs in yellow pigments in plants
O
OOH
OH
OHFLAVONE(APIGENIN)
FLAVONES CONT’D
• Flavones have a wide spectrum of biological activity-anti-tumor, anti-inflammatory. Also used as dyes in textile industry
O
OOH
OH
OH
OH
OH
FLAVONOL(QUERCETIN)
FLAVONES CONT’D
• Quercetin found in apples. Major constituent of red wine. Found to reduce incidences of cardiovascular diseases
O
OH
OH
OH
OH
OH
FLAVANOL eg catechin
Chroman, flavan, flavanol etc
• Constituent of vitamin E
O
3,4-Dihydro-2H-1-benzopyranCHROMANOR
Vitamin E
O
vitamin E
Flavan, flavanol
O
OH
O
FLAVANOLFLAVAN
DIBENZOPYRAN DERIVATIVES
O
HNO3
O
O
XANTHENE XANTHONE