Switching Between MHAT and Concerted Pathway: Ligand Controlled Regiodivergent Synthesis of Alkyl-Alkoxysilanes

Alkylsilanes (Csp3−Si(OR)3) possess a significant potential for forging Csp3−C bonds via cross- coupling reactions. Nonetheless, there is a paucity of alkyl−Si(OR)3 synthesis, and the existing literature protocols are unconvincing. Hydrofunctionalization via metal hydride alkene insertion is a highly effective way for forming Csp3−Csp3 bonds, although it does not extend to the synthesis of alkyl−Si(OR)3. In nearly all hydrofunctionalizations, the substrates dictate the stereochemical outcome (linear vs. branched), and a concerted pathway or more recently MHAT has been invoked to elucidate the reaction's stereochemistry. Ligand-controlled hydrometallation is scarce but provides significant advantages over substrate control. This work outlines a method for toggling between the concerted and MHAT pathways through a ligand modulation, yielding a very efficient regiodivergent synthesis of alkyl−Si(OEt)3 with sensitive functional groups and α-quaternary silicon. The mechanism by which a change in the ligand alters pathways was demonstrated through extensive experimental studies and DFT calculations.