Highly efficient Rh(I)/tris-binaphthyl monophosphite catalysts for hydroformylation of sterically hindered alkyl olefins

Abstract

The hydroformylation of highly substituted alkyl olefins was efficiently performed, with use of rhodium(I)/tris-binaphthyl monophosphite catalysts, containing different ether substituents at the 2′-binaphthyl position (OMe, OBn, OCHPh2 and OAdamantyl). A systematic kinetic study, carried out for hydroformylation of methyl non-3-enoate, has shown a significant influence of the ligand’s OR group in the performance of the rhodium catalysts, with Rh(I)/tris[2′-benzyloxy-1,1′-binaphthyl-2-yl]phosphite catalytic system (Rh(I)/L2-OBn) achieving the highest chemoselectivity for aldehydes, and regioselectivity for C-5 formyl products. This catalytic system was further applied to the hydroformylation of encumbered CC double bonds of natural products, namely oleic acid methyl ester, (−)-isopulegol benzyl ether and 17β-acetoxyandrost-4-ene, obtaining high catalytic activity, chemo-, regio- and diastereoselectivity, under relatively mild reaction conditions.