α-Trifluoromethyl-(indol-3-yl)methanols as trifluoromethylated C3 1,3-dipoles: [3+2] cycloaddition for the synthesis of 1-(trifluoromethyl)-cyclopenta[b]indole alkaloids

The first formal [3+2] cycloaddition using alpha-trifluoromethyl-(indol-3-yl)methanols as the trifluoromethylated C-3 1,3-dipoles for the construction of the five-membered carbocycle of 1-trifluoromethylated cyclopenta[b]indole alkaloids is described. An unprecedented step-wise dehydrative alkenylation of alpha-trifluoromethyl alcohols was revealed as the crucial transformation.