Dearomatization of 3-cyanoindoles by (3 + 2) cycloaddition: from batch to flow chemistry

Abstract

1,3-Dipolar dearomatizing cycloadditions between a non-stabilized azomethine ylide and 3-cyanoindoles or benzofuran afford the corresponding 3D-heterocycles bearing a quaternary carbon centre at the ring junction. While 6 equivalents of ylide precursor 1 are required for full conversion in a classical flask, working under flow conditions limits the excess (3 equiv., t^R = 1 min) and leads to a cleaner process, affording cycloadducts that are easier to isolate.