Methanolation of Olefins: Low-Pressure Synthesis of Alcohols by the Formal Addition of Methanol to Olefins

Abstract

Methanolation of olefins is introduced as a new low-pressure synthetic pathway to C1 elongated alcohols. Formally, H3COH is added to the C=C bond in a 100 % atom efficient manner. Mechanistically, the overall transformation occurs as a tandem reaction sequence by combining the dehydrogenation of methanol to syngas at a CO : H2 ratio of 1 : 2 with subsequent hydroformylation to the corresponding aldehyde and its final hydrogenation to the alcohol. The dehydrogenation and hydrogenation steps are catalyzed by a Mn/pincer complex, while the hydroformylation is accomplished by a Rh/phosphine catalyst. Using 1-octene as prototypical substrate, a yield of 80 % nonanol was achieved with a ratio of 93 : 7 of linear to branched alcohols and turnover numbers (TONRh) of more than 17 000 could be obtained in relation to the precious metal Rhodium. The integrated catalytic system provides direct access to alcohols from olefins and “green” methanol, avoiding the handling of pressurized CO and H2 and the use of specialized high-pressure equipment as the process conditions do not exceed 10 bar with partial pressures of syngas in the range of only 1–2 bar.