Issue Date: February 6, 2017
Chemists solve olefin hydration challenge
Building on recent developments in photoredox chemistry, a team led by Aiwen Lei of Wuhan University has found a new solution to one of chemistry’s long-standing synthetic challenges: the catalytic anti-Markovnikov hydration of olefins (ACS Catal. 2017, DOI: 10.1021/acscatal.6b03388). Direct addition of water to olefins to make alcohols is a well-developed industrial chemical reaction. For most olefins, this hydration process involves using an acid catalyst, such as sulfuric or phosphoric acid, and follows Markovnikov’s rule, in which the hydroxyl group bonds to the double-bond carbon that has the greater number of carbon–carbon bonds. For terminal olefins, the process produces secondary alcohols. The anti-Markovnikov hydration of olefins, in which the selectivity is reversed and the hydroxyl group bonds to the carbon on the other end of the double bond, converts terminal olefins to primary alcohols. But catalytic anti-Markovnikov olefin hydration is not straightforward; it requires indirect hydroboration/oxidation with borane reagents and peroxides or precious-metal catalysts. Those approaches can be costly, generate significant waste, or are hazardous on a large scale. Lei and coworkers found that a mesityl-substituted methylacridinum photocatalyst in conjunction with diphenyl disulfide as a hydrogen-transfer catalyst avoids those problems and delivers high yields of a variety of aliphatic and aromatic alcohols from terminal and internal olefins on a gram scale.
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