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Ligand-induced control of C-H versus aliphatic C-C migration reactions of Rh carbenoids
Maxime Vitale1, Thomas Lecourt, Chris G Sheldon
1School of Chemistry, University of Bristol, Cantock's Close, UK.
Abstract:
The reaction of lithiated trimethylsilyldiazomethane (LTMSD) with aldehydes and subsequent quenching with TMSCl furnished relatively stable alpha-silylated diazocompounds. Upon treatment of the alpha-silylated diazocompounds with Rh2(OAc)4 in refluxing toluene, alpha-silyl silyl enol ethers were formed from unbranched and branched aliphatic aldehydes through predominantly 1,2-migration of the C-H bond. In contrast, treatment of the alpha-silylated diazocompounds with Rh2(tfa)4 at room temperature gave alpha-silyl silyl enol ethers through exclusive and unusual 1,2-migration of the C-C bond. The origin of the selectivity observed from the two catalysts is discussed in relation to early and late transition states.
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