Perovskites catalyze aldehyde alkylations

Mention perovskites to C&EN readers, and many of them will think of solar cells—and for good reason: organolead halide compounds with the perovskite crystal structure and ABX₃ stoichiometry have been the superstars of low-cost photovoltaics for a few years running. A new study shows the perovskites have other tricks up their sleeves. A team led by San Diego State University chemists Xiaolin Zhu and Yong Yan reports that methylammonium lead tribromide and the cesium analog, two of the most studied solar-cell perovskites, double as highly active photocatalysts for organic synthesis (J. Am. Chem. Soc. 2019, DOI: 10.1021/jacs.8b08720). The researchers used standard methods to prepare the low-cost nanocrystal catalysts and explored their reactivity under blue-light illumination in tests with 2-bromoacetophenone and octanal. The reactions generated a mixture of products, including the aldehyde α-alkylation product (shown), other C-coupling products, and dehalogenated acetophenone. By tuning reaction conditions, the team was able to boost the selectivity of the industrially important α-alkylation reaction to 96%. The perovskites are 1,000 times as active as some iridium- and ruthenium-based catalysts and only a fraction of the cost, Yan points out.