Intramolecular Asymmetric Cyclopropanation Using Air-Stable Alkylboronic Esters

Abstract

The preparation of polysubstituted bicyclo[3.1.0]hexanes starting from air-stable substituted pent-4-en-1-ylboronic acid esters has been investigated. The method involves a Matteson homologation with LiCHCl₂, leading to 1-chlorohex-5-en-1-ylboronic acid ester intermediates. The subsequent intramolecular cyclopropanation step was performed in a one-pot process. With pinacol boronic esters, the cyclopropanation step was either performed thermally at 140 °C or at 70 °C after in situ transesterification to form a catechol boronic ester. This last approach is suitable for the preparation of enantioenriched bicyclo[3.1.0]hexanes using either chiral-auxiliary control or by taking advantage of the sparteine-controlled enantioselective boroalkylation of alcohols.

Key words

cyclopropanation - boronic esters - Matteson homologation - chloroalkylboronates - bicyclo[3.1.0]hexanes - fused cyclopropanes

Publication History

Received: 27 July 2023

Accepted after revision: 22 August 2023

Accepted Manuscript online:
22 August 2023

Article published online:
28 September 2023

• References and Notes

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