Acid- or base-promoted photostimulated homolytic tert-butylation of pyridines and thiophenes

摘要

Regioselective photostimulated homolytic tert-butylations for heteroaromatics such as pyridines or thiophenes areninvestigated with tert-butylmercury() chloride in the presence of toluene-p-sulfonic acid (PTSA) or 1,4-diazabicyclo[n2.2.2]octane (DABCO) respectively. While the promotion effect of acid is quite strong for basic pyridines, thenacid does not promote the reaction effectively for non-basic thiophenes. On the other hand, pyridines and thiophenesnexhibit similar tendency for the base-promoted homolytic tert-butylations, and the reactivity is mainly controlled bynsubstituent carbonyl or cyano groups as well as by regioselectivity.