Homologation of Alkyl Acetates, Alkyl Ethers, Acetals, and Ketals by Formal Insertion of Diazo Compounds into a Carbon-Carbon Bond

Homologation of alkyl acetates, alkyl ethers, acetals, and ketals was accomplished via formal insertion of diazo esters into carbon-carbon sigma-bonds. The combined Lewis acid InI3 with Me-3 SiBr catalyzed the homologation of alkyl acetates and alkyl ethers. That of acetals and ketals was catalyzed solely by the use of InBr3. The key point of the homologation mechanism is that the indium-based Lewis acids have the appropriate amount of Lewis acidity to achieve both the abstraction and release of leaving groups. The abstraction of a leaving group by an indium-based Lewis acid and the electrophilic addition of carbocation or oxonium intermediates to diazo esters followed by the rearrangement of carbon substituents provide the corresponding cation intermediates. Finally, the leaving group that is captured by the Lewis acid bonds with cation intermediates to furnish the homologated products.

Automated summary

The homologation of alkyl acetates, alkyl ethers, acetals, and ketals was achieved through the formal insertion of diazo esters into carbon-carbon sigma-bonds. The use of the Lewis acids InI3 with Me-3SiBr catalyzed the homologation of alkyl acetates and alkyl ethers, while InBr3 catalyzed that of acetals and ketals. The appropriate Lewis acidity of the indium-based Lewis acids played a key role in both the abstraction and release of leaving groups, leading to the formation of homologated products.