MIRC reactions using sulfoxides and synthesis of dictyopterene A

Abstract

Michael initiated ring closure reactions, using alkyl imidazolyl sulfoxides as nucleophiles, provided a 2-substituted cyclopropanecarboxylate 2 and cyclohexanecarboxylate 5, with high yields and excellent diastereoselectivity. Thermal elimination of the imidazolylsulfinyl group gave an alkene 3. This method was used to carry out a short synthesis of dictyopterene A. A 2-hexenylcyclopropanecarboxylate 13 was prepared using a MIRC reaction of hexyl 1-methyl-2-imidazolyl sulfoxide with 4-bromocrotonate, followed by pyrolytic elimination of the imidazolylsulfinyl group. Straightforward conversion of the ester group into a vinyl group furnished dictyopterene A.