Highly Selective Hydroaminomethylation of Internal Alkenes To Give Linear Amines

The application of phenoxaphosphino‐modified Xantphos‐type ligands (1–9) in the rhodium‐catalyzed hydroaminomethylation of internal olefins to give linear amines is reported. Excellent chemo‐ and regioselectivities have been obtained through the use of 0.1 mol % [Rh(cod)2]BF4/0.4 mol % xantphenoxaphos (1), providing a practical and environmentally attractive synthetic route for the preparation of amines from internal alkenes. For the first time, both functionalized internal olefins and mixtures of internal and terminal olefins have been converted highly selectively into linear amines. Investigations of the effects of the calculated natural bite angles of ligands on hydroaminomethylation shows that the regioselectivity for the linear product follows a similar trend to that seen in the hydroformylation of internal alkenes with the aid of these ligands. Hydroaminomethylation and each of its individual steps were monitored by high‐pressure infrared spectroscopy. The results suggest that hydroaminomethylations take place by a sequential isomerization/hydroformylation/amination/hydrogenation pathway. High yields and unprecedentedly high regioselectivities (up to 96 %) have been achieved for the hydroaminomethylation of functionalized internal olefins by using a new rhodium‐based catalyst system (see scheme). Remarkably, an industrial octene mixture is also selectively hydroaminomethylated to provide the linear amine.