Domino reaction sequences in the rhodium-catalyzed hydroformylation of 3-acetyl-1-allylpyrrole: a short route to 5,6,7,8-tetrahydroindolizines

The rhodium-catalyzed hydroformylation of 3-acetyl-1-allylpyrrole (1) gives an equimolar mixture of the tetrahydroindolizines 2 and 3 via two different domino processes. Interestingly, 3 forms via a stabilized 8-hydroxyindolizine which, although often postulated as an intermediate in the cyclization mechanism under oxo conditions, has been isolated and characterized here for the first time.