PPh2H-involving mixed ligands-controlled Rh-catalyzed iso-selective hydroformylation of 1,3-butadiene

Abstract

The hydroformylation of olefins is a cornerstone of homogeneous catalysis and industrial chemistry, yet achieving precise regioselectivity, particularly for 1,3-butadiene, remains a formidable challenge. Here we introduce a transformative rhodium-based catalytic system that achieves unprecedented efficiency in the hydroformylation of 1,3-butadiene, yielding dialdehydes with exceptional efficiency (up to 88 %). Our strategy employs a mixed dual-ligand system combining a tetradentate phosphine ligand and a diphenylphosphane, which synergistically facilitate the two-stage hydroformylation process during the catalytic cycle of CO insertion. This cooperative function of mixed ligands enables the selective production of 2-ethylbutanedial with a record-breaking iso-selectivity of up to 67.8 %. Mechanistic investigations, supported by computational and experimental studies, reveal the critical and competitive role of binary mixed-ligand catalysis (BMLC) and ligand-relay catalysis (LRC) in this reaction. Specifically, three coordination modes derived from multidentate phosphine and monodentate diphenylphosphane ligands alternately govern key steps of the catalytic cycle, including olefin activation and regioselective insertion.