Regioselective Oxidative Ring Opening of Cyclopropyl Silyl Ethers: A Quantum Chemical Study

Abstract

In contrast to the structurally and configurationally stable alkyl‐ or aryl‐substituted cyclopropyl radical cations, cyclopropyl silyl ethers undergo spontaneous ring opening upon oxidation whereby the endocyclic CC(O‐TMS) bond is cleaved with remarkable selectivity. DFT calculations on 1‐trimethylsilyloxybicyclo[4.1.0]heptane show that this selectivity arises from the topology of the potential surface of the corresponding radical cation which is initially generated in a very steep region of the potential surface from where the steepest descent leads to cleavage of the endocyclic rather than the lateral CC(OTMS) bond. Cleavage of the lateral bond leads to interesting conformational changes which are explored in detail.

Selective Carbon–Carbon Bond Cleavage of Cyclopropanols

“…Recently, in their synthesis of GB22, Shenvi and co-workers outlined an Ir/Ni cocatalyzed coupling of ring-expanded β-keto radicals derived indanone-based siloxycyclopropanes ( 431 ) with aryl bromides and iodides 432 (Scheme ). − From the perspective of preparing substrates such as 433 , this bond disconnection strategy is synthetically useful; the corresponding conjugate addition is challenging, since the Michael acceptor exists predominantly as the phenol tautomer. In this case, the photoexcited Ir catalyst oxidizes 431 to form a siloxycyclopropane radical cation, which results in desilylation and the formation of a β-keto radical.…”