1,3-Dipolar character of six-membered aromatic rings. Part 44. Further examples of troponoid synthesis

Abstract

Adducts formed from 3-hydroxypyridine and two moles of the dipolarophiles, acrylonitrile and methyl acrylate, are converted by quaternisation and Hofmann elimination into 4-cyanotropolone and 4-methoxycarbonyltropolone. Overall yields of ca. 25% are achieved in one-pot reactions from 3-hydroxypyridine 2-Chloro-, 2-bromo-, and 2-cyano-1-methyl-3-oxidopyridinium form adducts with 2π addends, some of which were converted into tropone derivatives.