Progress in the synthesis of aldehydes from Pd-catalyzed Wacker-type reactions of terminal olefins

Wacker-type reactions of terminal alkenes mainly lead to methyl ketones rather than aldehydes. The selective formation aldehydes usually requires containing a suitable coordinating fragment. A few procedures however provide fair high aldehyde/methyl ketone ratios in the absence directing group. This review, which is focused on aldehydes, summarizes methods reported since 2007 and, with personal comments, mechanisms and intermediates proposed rationalize regioselectivity.