Regioselective Hydroxymethylation of Alkenes to Linear Alcohols with CO₂/H₂ Using a Rh/Ru Dual Catalyst

Abstract

CO 2 is an attractive renewable C1 resource, and H 2 is a cheap and green reductant. The combination of CO 2 and H 2 for hydroxymethylation of alkenes provides a novel synthetic tool to directly generate alcohols, especially linear ones, which are generally preferred as precursors of detergents and plasticizers. However, the most problematic issue of this promising transformation is the non-regioselection due to the inability of regioselectivity control over the ligand, resulting from the high temperature required for the reverse water−gas shift step. Here, we develop an innovative strategy to selectively produce linear alcohols from alkenes and CO 2 /H 2 through the regiocontrollable ability of the ligand. The reaction is efficiently mediated by a bimetallic Rh− Ru catalyst using PTA (1,3,5-triaza-7-phosphaadamantane) as the ligand, and the desired alcohols can be obtained in up to 92% yield with 87/13 regioselectivity, which surpasses that ever reported. The mechanistic study reveals that the transformation proceeds through domino sequences, that is, CO 2 hydrogenation to HCOOH, fast release of CO, hydroformylation, and aldehyde reduction. The synergy of Rh and Ru contributes to the excellent fulfillment of the domino sequences, while the ligand PTA regulates the regioselectivity elegantly. Notably, the preferred hydrogenation of CO 2 and aldehydes by Ru/PTA inhibits the occurrence of alkene isomerization and hydrogenation, which is not available in other ligands. The strategy opens a new way for selective production of linear alcohols together with CO 2 transformation through the regiocontrollable ability of the ligand, which will shed light on industrial carbonylation with CO 2 .

Advancements and Challenges in Reductive Conversion of Carbon Dioxide via Thermo-/Photocatalysis

“…Besides amines, C-, O-, and S- nucleophiles can also be applied to the CO 2 reductive functionalization to form C–C, C–O, and C–S bonds, but these weak nucleophiles result in only a few examples including hydroxymethylated, hydroformylated, alkoxycarbonylated, C-methylated, O-formylated, O/S-methylated, and S-methylenated products, secondary alcohol, or formamidine derivatives …”

Iron-catalyzed β-hydroxymethylative carbonylation of styrene under photo-irradiation

“…To the best of our knowledge, a typical emphasis in past decades was placed on exploiting various C1 synthons, 4 and pleasingly, C1 synthons including CO, 5 CO 2 , 6 HCHO, 7 and isocyanides 8 have been used as efficient building blocks in many established transformations. Probably due to easy accessibility, reactions involving double bonds with C1 synthons have been deeply investigated, 9 and diverse elegant reactions have been reported thus far. For example, both the Prins reaction and Alder–ene reaction represented the addition of styrene to formaldehyde (Scheme 1, eqn (a)).…”