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Benzopyrylium salt and Benzopyrones
Many compounds belonging to these classes are found in plant
kingdom .Most red and blue flowers petals contain anthocyanins
,derivatives of benzopyrylium cation ( 1 ) ,as the coloured material ,
and the yellow benzo – 2 – (2) and – 4 – pyrones ( 3 ) are also
widely distributed .
O
+
(1)
O
(2)
O
O
O
O
(3)
(4)
Reduction product of these compound ,which can be treated as
derivatives of benzopyran ( 4 ) are also common plant constituents
.
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The anthocyanine :
The anthocyanine is hydroxylated derivatives of the benzopyrylium
cation e.g. Pelargonidin ( 5 ) and cyanidin ( 6 )
HO
HO
ClO
+
OH
HO
ClO
+
OH
Pelargonidin
OH
OH
OH
(5)
OH
Cyanidin
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(6)
2
Ring synthesis of benzopyrylium
From phenols and 1,3 – dicarbonyl compounds
CH3
CH3
HO
OH
+
ACOH / HCl
O=C
CH2
HO
Resorcinol
+
O
MeCl-
O = C - Me
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Mechanism
H
HO
HO
HO
CH3
CH3
O=C
HO- C
CH3
CH
+CH
CH2
OH
3
C
HO
O = C - Me
C
CH
O
=
C
Me
ACOH / HCl
CH
..
|
|
HO
OH C - Me
OH C - Me
OH
O-
CH3
C
CH
|
OH C - Me
O
Me
C
CH
+C
O Me
Cl-
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Benzo – 2 – pyrones
Benzo – 2 – pyrone commonly called coumarin , is the sweet
smelling constituents of white clover .A considerable number of
hydroxy and methoxy – coumarins , and their glucosides , have
been isolated from plant sources .
O
O
O
-
NaOH
CH
-
CO2
CH + 2 Na+
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Synthesis of coumarin
Coumarin can be synthesized from salicylaldehyde by a Perkin reaction
OH
O
AC2O
NaOAC
O
CHO
Mechanism
O
O
1 - CH3 - C - O - C - CH3 + NaOAC
O
O
-
CH2 - C - O - C - CH3 + ACOH
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OH
2-
O
CH3
O
+C
O
OH C = O
O- CH
2
C
H
O
-
+ :CH2 - C - O - C - CH3 + ACOH
C=O
+H
CH3
O
-
+C
-
O
C=O
OH
O
C=O
OH
O CH
2
CH
CH
O
C
O
OH C = O
CH2
-
O
+
CH-3 C - O - C - CH3
CH2
O
CH3
O
C CH3
||
O
CH3
O
C
O
O
OH C = O
+ CH3 - C - O -
CH
O - C - CH3
+ CH3COOH
:CH
CH
O - C - CH3
O
O
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CH3
O
C
O
OH C = O
O
C=O
- CH3COOH
CH
CH
CH
CH
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Benzo – 4 – pyrones .
Benzo – 4 – pyrones or chromones has not yet been isolated from
natural sources , although a few hydroxyl derivative occure in
certain plant .In contrast many 2 – phenyl – Benzo – 4 – pyrones
usually called flavones and their glycosides and a considerable
number of isoflavones have been identified in plant extracts
O
Ph
O
Ph
O
2 - phenyl benzo 4 - pyrones falvones
O
3 - phenyl benzo 4 - pyrones isofalvones
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Synthesis
2 – Hydroxy acetophenone with benzaldehyde and basic catalyst
gives the unsaturated ketone ( 1) cyclization with acid gives
flavone
O
C
OH
C
O
CH3
+
H
O: + CHPh
-CH
C
O
H
OH CHPh
CH
C
O
base
O
C
O
HCl
EtOH
O
CHPh
CH2
Ph
-H2
Oxidation
O
falvones
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Heterocyclic analogues of Cyclopropane
All three membered rings have one major property in common- a strained ring
which confers great reactivity on the compounds in comparison with their openchain analogues.
AZIRIDINE
Aziridine or ethylenimine and occasionally as azacyclopropane was first obtained
by Gabrial in 1888, ethylenimine and its derivatives has increased greatly in
recent years, and these compounds have much academic and industrial
importance today.
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Chemical properties
Aziridine is not very stable its best stored over sodium hydroxide in
refrigerator. It has a number of reactions of secondary amines.
1. As a secondary amines Aziridine add activated double bounds.
H
N
+
CH2=CHCN
N-CH2-CH2-CN
2. Treatment of Aziridine with methyl iodide opens the ring.
H
N
CH3I
+
CH3NCH2CH2II
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3. Polymerisation :Aziridine polymerises in the presence of trace of water and rapidly explosive
in presence of acids.
H
+
H
H
N
H2
+ N
NH2
CH2
N
+
CH2
NHCH2CH2NH2
n
n
H
N
POLYMER
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4. Aqueous hydrochloric acid open the Aziridine ring to give 2-chloro
ethylamine which react with NaoH to give back aziridine.
H
N
+
CL-CH2-CH2-NH3-CL
HCL
NaOH
5. Dialkyl aminoethyl chloride are well known for dimerising to the cyclic bis
quaternary salt via reaction of the halid with a cation molecule.
R2
+N
R2
N+
X
2CL
N+
R2
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6. Diphenyl acetonitrile react with 2- chloro-1- dimethylaminopropane and 1chloro 2- dimethylamino propane in presence of pot-t-but oxide to give both IV
and V when Aziridine cation react with the same reagent the ring open giving
the same product.
Ph- C-CN
CH3NCH2CHClMe
Me-CH-CH2-N-Me2
II
CH3
Ph2-CH-CN
N
CH3
CL-CH2-CH-Me-N-Me2
III
Ph-C-CN
CH2-CH-N-CH3
CH3
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7. Aziridne react with hydrogen sulphide to give 2,2- diaminodiethyl sulphide.
H
N
+ S2 H
( H2NCH2CH2) 2S
8. Aziridine react with vigorously carbondisulphide to give 2- thia thaizolidone.
H
N
CS2
CSS
4
H
N3
N
5
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S
1
2
S
16
9. Aziridine react with acetone and some other aldehyde and Keton to give
oxazolidinesals 5– 10 C
o
H
N
+
4
RCOR
5
H
N 3
O
1
2
RR'
10. Necleophilic reagent:
Aziridine react with ammonia to give, 1,2-di-amino with SN2 mechanism.
H
N
+
NH2-CH2-CH2-NH2
NH3
In presence of acid its give drevative of alcohol amine.
+
H
N
+
+
H3O
H2
+
N
H2O
+
OH
H2O
NH2
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+NH
3
17
Reduction:Aziridine reduce with hydrogen in presence of Rany pickle giving
t. butylamine while in presences of methyl lithium it gives N-lithum derivative.
H
Li
CH3Li
N
Me
N
Me
Me
Me
H2
Raney Ni
(CH3)3-C-NH2
11. The highly medication activity of aziridine is altnibuted to its ability to alkylat
compound even in bio condition e.g. Aziridine react with the amino acid Methionine
in aqueous medium of ph 7.4 to give soluble salt.
CH2-CH2-NH-R
R2
N
R
+
MeS-(CH2)-CH-COOH
NH2
Me-S-(CH2)2-CH-COOH
+
NH2
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12. Aziridine when reacted with nucleophilic reagent containing hydrogen atom
its give amide while its give acid when the reagent doesn't cotain hydrogen.
Ph-CH-(OBut)-CO-NH-But
But
N
ButOH
Ph
-+
Butok
O
HCl
Ph-CH-(NH-But)COOH
13. Aziridine react with electrophilic reagent for example
a-
b-
NH
NH
+
+
NEt3
CL-CH2-COOEt
CH2=CH-CN
NCH2COOEt
N-CH2-CH2-CN
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Synthesis:From α – amino alcohol with H2So4
OSO3H
OH
H2SO4
C6H5-CH-CH2-NH2
C6H5-CH-CH2
HO-SO3H
-H2O
NH2
..
H
NaOH
N
C6H5
-H2SO4
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1. Gabriel Method:From α – amino alcohol with thionyl chloride.
H
SOCl2
H2N-CH2-CH2-OH
+
NH3-CH2-CH2-CL-CL
N
2. From aryl alkyl ketoximes when react with alkyl or aryl magnesium halides
MgBrNOH
NOH
Ph-C-Me
EtMgBr
H
Ph
N
Ph-C-Me
Et
Et
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