An improved ring-closing metathesis approach to fluorinated and trifluoromethylated nitrogen heterocycles

The synthesis of fluoro- and trifluoromethyl-containing N-sulfonylated nitrogen heterocycles is described. A first crucial step is a Mitsunobu functionalization of intermediate sulfonamides using commercially available unsaturated alcohols, which gives efficient access to fluorinated ring-closing metathesis (RCM) precursors. Key step is an RCM reaction of these precursors leading to the corresponding fluoro- and trifluoromethyl-containing heterocyclic building blocks. Furthermore, aminopalladation of the same sulfonamide intermediates provides access to trifluoromethyl-containing pyrrole derivatives. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).