Revisiting the Mg/TMSCl/Dipolar Solvent System for Dearomatic Silylation of Aryl Carbonyl Compounds: Substrate Scope, Transformations, and Mechanistic Studies

Abstract

Dearomatic silylation of arene derivatives is an intriguing synthetic target, which represents an elegant extension of Birch reduction and produces silylated cyclohexene derivatives with great potential of further transformation. Herein, we report a systematic study on dearomatic silylation of aryl carbonyl compounds with Mg and the TMSCl/NMP adduct. The protocol displays a wide range of substrate scope, including alkyl aryl ketones, aromatic amides, benzonitriles, tert-butyl benzoates, and even 2,2′-bipyridines. Synthetic utility is demonstrated using the products as versatile substrate in various transformations. The detailed mechanism is presented with both control experimental analyses and theoretical calculations. An unusual five-coordinated silicon dianion intermediate is first proposed and described here. The selectivity is influenced by the relative rates of single electron reductions (the TMSCl/NMP adduct versus the substrate) and the steric effects.

Reduced 2,2’‐Bipyridine Lanthanide Metallocenes Provide Access to Mono‐C5Me5 and Polyazide Complexes

“…The reaction is further complicated by the trimethylsilyl substitution byproduct. Alkylation of bipyridine is known through its reaction with alkyllithium reagents [59] and silylation of bipyridyl carbons is possible through a variety of means [60–62] . However, the silylation of bipyridine by its reaction with trimethylsilylazide is highly unusual and highlights the difficulty of predicting the outcome of these reactions, even when the stoichiometry is carefully controlled.…”