Thionyl Chloride-induced Conversion of 1-Ethyl-1,4-dihydro-2-methyl-4-oxoquinoline-3-carboxylic Acids to Highly Functionalised Thieno[3,4-b]quinoline Derivatives

Abstract

Warming a title acid with SOCl₂ gives the corresponding 3,3,9-trichlorothieno[3,4-b]quinolin-1(3H)-one whereas reaction at room temperature leads to the intermediate 3,3-dichloro-4-ethylthieno[3,4-b]quinoline-1(3H),9(4H)-dione product as established from the respective X-ray crystallographic determinations.