Utility of isothiocyanates in heterocyclic synthesis

Abstract

Reaction of substituted pyrazolin-5-one and 3-phenyl-5-isoxazolone 1a-c with phenyl isothiocyanate in basic DMF gave the non-isolable sodium salt of the adduct 2a-c which was treated with HCl to give the corresponding thiocarbamoyl derivatives 3a-c . The latter compounds underwent heterocyclization upon treatment with chloroacetyl chloride and ethyl bromoacetate to give the corresponding thiazolidinone derivatives 6 and 7 . Compound 3a,b was oxidized to yield benzothiazoly pyrazolinone derivatives 8a,b . Also, nucleophilic substitution of 2 and 3 and with different nucleophilic reagents afforded the products 9-14 . Cyclocondensation of the thiocarbamoyl salt with some halogenated esters or acid chloride derivatives such as f -bromopropionate, ethyl chloroformate and f -bromo diethyl malonate afforded cyclized polyfunctionally thiazinone, thiazetidinone and thiazolidinone derivatives respectively 15-17 . The structures of the products were confirmed by spectral and micro analytical data.