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Chemoselective P(NMe2)3‑Mediated Reductive Epoxidation between Two Different Carbonyl Electrophiles: Synthesis of Highly Functionalized Unsymmetrical Epoxides

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posted on 05.06.2018, 00:00 by Rong Zhou, Honghui Zhang, Jialin Liu, Rongfang Liu, Wen-Chao Gao, Yan Qiao, Ruifeng Li
Herein, we report a chemoselective P­(NMe2)3-mediated reductive epoxidation of α-dicarbonyl compounds such as isatins, α-keto esters, and α-diketones with aldehydes and ketones, leading to an efficient synthesis of a wide range of highly functionalized unsymmetrical epoxides in moderate to excellent yields and diastereoselectivities. The Kukhtin–Ramirez adduct, which is exclusively generated in situ from an α-dicarbonyl compound and P­(NMe2)3, plays a key role in governing the chemoselectivity. It represents the first practical synthesis of unsymmetrical epoxides via direct reductive epoxidation of two different carbonyl electrophiles and also complements the existing methods of generating epoxides.