Reaction of 1-[2-(vinyloxy)ethyl]-1H-pyrroles with trifluoroacetic anhydride

Chemo- and stereoselectivity of the reaction of 1-[2-(vinyloxy)ethyl]-1 H -pyrroles with trifluoroacetic anhydride have been studied. The reaction with an equimolar amount of trifluoroacetic anhydride chemoselectively involves the free α-position of the pyrrole ring with formation of the corresponding α-trifluoroacetylpyrroles. In the reaction with 2 equiv of trifluoroacetic anhydride, acylation of both α-position of the pyrrole ring and β-position of the vinyloxy group leads to the formation of 1-(2-{[(1 E )-4,4,4-trifluoro-3-oxobut-1-en-1-yl]oxy}ethyl)-2-trifluoroacetyl derivatives with high stereoselectivity.