Trifluorodiazoethane (CF3CHN2) in the Uncatalyzed Cyclopropanation of 3-Arylmethylenebenzofuran-2(3H)-ones

摘要

The uncatalyzed cyclopropanation of 2,2,2-trifluorodiazoethane onto 3-arylmethylenebenzofuran-2(3H)-ones leads to highly functionalized trifluoromethylated spirocyclopropanes. A thermal activation mode not requiring the addition of a transition metal provided high product yields, whereas a salt effect benefited the diastereomeric ratios obtained. The products are readily elaborated to non-spiro derivatives.