Recent Advances in α-Alkylation Reactions using Alcohols with Hydrogen Borrowing Methodologies

This paper summarizes recent advances in a-alkylation reactions based on hydrogen borrowing methodologies using alcohol as an alkylating agent. This review provides a summary of recent progress toward the a-alkylation of carbonyl substrates, as well as relatively unactivated substrates bearing fewer acidic a-hydrogens, such as acetonitriles, acetamides, esters, methylpyrimidines, and methylquinolines. A summary of recent improvements in a-methylation strategies based on hydrogen borrowing methodologies has also been provided. Particular emphasis has been placed on highly practical and green chemistry approaches involving modified catalytic systems, including metal-supported heterogeneous catalysts and nanoparticle-based catalysts, as well as reactions conducted in the absence of a transition-metal catalyst. A review of recent achievements in methylation strategies using methanol as a methyl source, and their application to the a-methylation of ketones using transition-metal catalyzed hydrogen borrowing methodology, has also been documented.