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

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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
. 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 )
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Ring synthesis of benzopyrylium
From phenols and 1,3 dicarbonyl compounds
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Mechanism
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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 .
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Synthesis of coumarin
Coumarin can be synthesized from salicylaldehyde
by a Perkin reaction
Mechanism
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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
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Synthesis
2 Hydroxy acetophenone with benzaldehyde and
basic catalyst gives the unsaturated ketone ( 1)
cyclization with acid gives flavone
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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 open-chain 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.
2. Treatment of Aziridine with methyl iodide
opens the ring.
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3. Polymerisation -
Aziridine polymerises in the presence of trace of
water and rapidly explosive in presence of acids.
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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.
5. Dialkyl aminoethyl chloride are well known for
dimerising to the cyclic bis quaternary salt via
reaction of the halid with a cation molecule.
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6. Diphenyl acetonitrile react with 2- chloro-1-
dimethylaminopropane and 1- chloro 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.
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• 7. Aziridne react with hydrogen sulphide to give
  2,2- diaminodiethyl sulphide.
• 8. Aziridine react with vigorously
  carbondisulphide to give 2- thia thaizolidone.

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9. Aziridine react with acetone and some other
aldehyde and Keton to give oxazolidinesals 5 10
Co
10. Necleophilic reagent Aziridine react with
ammonia to give, 1,2-di-amino with SN2
mechanism.
In presence of acid its give drevative of alcohol
amine.
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Reduction-
Aziridine reduce with hydrogen in presence of
Rany pickle giving t. butylamine while in
presences of methyl lithium it gives N-lithum
derivative.
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.
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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.
13. Aziridine react with electrophilic reagent
for example
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Synthesis- From a amino alcohol with H2So4
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1. Gabriel Method-
From a amino alcohol with thionyl chloride.
2. From aryl alkyl ketoximes when react with
alkyl or aryl magnesium halides