Conversion of 4-oxoproline esters to 4-substituted pyrrole-2-carboxylic acid esters.

The Grignard, Wittig, Tebbe, Horner-Emmons, and Reformatsky reactions of the 4-oxoproline esters gave the corresponding 4-alylated or 4-alkylidenated products, respectively. The products were properly treated with bases to cause aromatization, giving 4-substituted pyrrole-2-carboxylic acid esters such as methyl 4-methylpyrrole-2-carboxylate, which is a trail pheromone of Atta texana.