2‐Arylsilacyclobutane as a Latent Carbanion Reacting with CO₂

Abstract

An electronically neutral 2-arylsilacyclobutane generates a nucleophilic carbanion at room temperature through cleavage of the benzylic C-Si bond when simply dissolved in polar aprotic solvents such as N,N-dimethylformamide (DMF). The nucleophilic species is capable of capturing carbon dioxide to furnish a silalactone. The carboxylation reaction is unique in that no additional activating agents are required.

A Combined Computational and Experimental Study of Rh-Catalyzed C–H Silylation with Silacyclobutanes: Insights Leading to a More Efficient Catalyst System

“…Due to their strain-release Lewis acidity, SCBs have also been employed in Mukaiyama aldol reactions , and Hiyama–Denmark cross-couplings . The most interesting class of transformations of SCBs is perhaps transition-metal-catalyzed reactions with unsaturated carbon–carbon bonds or small-ring compounds, as manifested in either a ring-opening manner or a formal cycloaddition manner. − These reactions are proposed to involve five-membered metallocycle intermediates via oxidative insertion into the SCBs, followed by the migratory insertion of the unsaturated carbon–carbon bonds to form ring-expansion intermediates. From there, the fates of the ring-expansion intermediates could diverge from β-hydride (β-H) elimination (ring-opening manner; giving acyclic products) to reductive elimination (cycloaddition manner; giving cyclic products).…”

Silacyclization through palladium-catalyzed intermolecular silicon-based C(sp2)–C(sp3) cross-coupling

“…Addition of a small amount of DMF would facilitate opening of the strained four-membered SCB 2a via transient coordination with the silicon atom. 10 However, the use of DMF as the solvent would lead to the consumption of the product 3aa during the reaction. Replacement of Pd(MeCN) 2 Cl 2 with [Pd(allyl)Cl] 2 or Pd 2 (dba) 3 resulted in a decrease in the yield (entries 10 and 11).…”

Recent advances in the reactions of silacyclobutanes and their applications

“…In 2018, a ring-opening/carboxylation reaction between CO 2 gas and silacyclobutanes was disclosed by Murakami and coworkers (Scheme 23). 47 In this transformation, no additional catalyst was required during the carboxylation process. Various 2-arylsilacyclobutanes 47 reacted with carbon dioxide in DMF leading to the silalactone 48 , which could be easily converted to the siloxane dimer of carboxylic acid 49 in the presence of water.…”