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 . lec11

The anthocyanine : The anthocyanine is hydroxylated derivatives of the benzopyrylium cation e.g. Pelargonidin ( 5 ) and cyanidin ( 6 ) lec11

Ring synthesis of benzopyrylium From phenols and 1,3 – dicarbonyl compounds lec11

Mechanism lec11

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 . lec11

Synthesis of coumarin Mechanism Coumarin can be synthesized from salicylaldehyde by a Perkin reaction Mechanism lec11

O C H CH = | + CH 3 - C - O - O + C H CH = : - + - C - O - C - CH 2 - C - O - C - CH | + CH 3 - C - O - O + C H CH = 2 : lec11

lec11

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 lec11

Synthesis 2 – Hydroxy acetophenone with benzaldehyde and basic catalyst gives the unsaturated ketone ( 1) cyclization with acid gives flavone lec11

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. lec11

1. As a secondary amines Aziridine add activated double bounds. 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. lec11

3. Polymerisation :- Aziridine polymerises in the presence of trace of water and rapidly explosive in presence of acids. lec11

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. lec11

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. lec11

7. Aziridne react with hydrogen sulphide to give 2,2- diaminodiethyl sulphide. 8. Aziridine react with vigorously carbondisulphide to give 2- thia thaizolidone. lec11

10. Necleophilic reagent: 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. lec11

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. lec11

13. Aziridine react with electrophilic reagent for example 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 lec11

Synthesis:- From α – amino alcohol with H2So4 lec11

1. Gabriel Method:- From α – amino alcohol with thionyl chloride. 2. From aryl alkyl ketoximes when react with alkyl or aryl magnesium halides lec11