Formation of Cyclopentanes and Cyclopropanes through Alkylation of Benzylic Anions using Ethers, Thioethers and Alcohols as substrates under Grubbs-Stoltz (Et3SiH/KOtBu) conditions.

Abstract

Reaction of diarylmethanes with the Grubbs-Stoltz reagent (KOtBu + Et₃SiH) using THF as solvent led to diarylcyclopentanes through an unprecedented double-alkylation reaction, with four of the carbons of the cyclopentane coming from THF. In like manner, reaction of diarylmethanes with the same reagent in 1,4-dioxane as solvent led to double-alkylation to form diarylcyclopropanes, with two of the cyclopropane carbons coming from 1,4-dioxane. Monoalkylated substrates that were likely intermediates on the dialkylation pathway were subjected to the same conditions, leading to cyclisations to form cyclopentanes and cyclopropanes. The cyclisation chemistry also extended to formation of monoarylcyclopropanes from reaction of the corresponding benzylpotassium reagents with ethers, alcohols, sulfides, sulfoxides and sulfones.