Transformation of Acyl Silanes to Carbanions Via a SET Mechanism

Yevgeni Mashin,Lieby Zborovsky, Boris Tumanskii, Dmitry Bravo-Zhivotovskii and Yitzhak Apeloig, Schulich Faculty of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, Technion-Israel Institute of Technology, Haifa , Israel, Technion, Haifa, Israel

α-silyl carbanions are  important synthons in organic synthesis. We present a "one flask" synthesis of unique non-solvated α-silyl organolithium compounds of type 2 (Scheme).Acyl silane 1 reacts with 2 molecules of tBuMe2SiLi (2b) to yield α-silyl carbanion 2 (X-ray).We suggest that this reaction occurs via a SET reduction of 1 by 2a to produce the dimeric  triplet biradical intermediate 3a (EPR) which further reacts with 2b to yield 2. Thus, triplet biradical 3a, prepared independently in reaction of 1 with 2a and isolated as a stable salt (X-ray), reacts via a co-aggregated species 3b (EPR) with silyl radical 4 (generated in-situ from (tBuMe2Si)2Hg), eliminating tBuMe2SiOLi to yield 2.

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