Cuprous bromide-promoted cyclization of ketene N,S-acetals with prop-2-ynyl bromide: synthesis of regiospecifically substituted and annelated 3-acyl(or nitro)-5-methyl pyrroles
Abstract
Acyclic 10a–h and cyclic 14a–b acyl and nitroketene 12a–bN,S-acetals undergo facile cuprous bromide induced cyclization with prop-2-ynyl bromide to afford 1-substituted-3-acyl(or nitro)-5-methyl-2-(methylsulfanyl)pyrroles 11a–h and 13a–b and the corresponding annelated analogues 15a–b in good yields.