Competitive free radical 4-nitrophenylation of pyridine and thiophene

Competitive free radical 4-nitrophenylation of pyridine and thiophene shows a relative reactivity of thiophene:pyridine of 1.3:1 as based on product isolation. A three-center reaction is proposed to account for the predominance of alpha substitution in each system. Column chromatography and ¹H nmr are used for separation and identification of products.