Simmons–Smith Cyclopropanation of Alkenyl 1,2-Bis(boronates): Stereoselective Access to Functionalized Cyclopropyl Derivatives

Abstract

A Simmons−Smith stereodefined procedure for the synthesis of cyclopropyl-1,2-bis(boronates) has been developed starting from the corresponding alkenes. The resulting compounds were then subjected to regioselective Suzuki−Miyaura couplings to produce diversely tri-or tetra-substituted arylcyclopropanes in good yields. Further functionalization with 2-lithiothiophene provided 1,2-bis(aryl)cyclopropanes. Article pubs.acs.org/joc

Enantioselective Suzuki cross-coupling of 1,2-diboryl cyclopropanes

“…When we started our study, we realized that bis-boryl cyclopropanes such as 2 had not been prepared in the literature before. 17,18 We envisioned that diboration of readily available cyclopropenes 1 could provide easy access to these intermediates. Our first attempts using Pt-catalyzed diboration conditions 19,20 afforded a complex crude product from which we isolated a 65 : 35 mixture of diborylated diastereomers 2a / 2a′ in 11% yield.…”

Regio- and stereocontrolled synthesis of borylated E-enynes, Z-enediynes and derivatives from alkenyl-1,2-bis-(boronates)

“…Finally, to obtain alkynylcyclopropylboronate 10 , 29 boronic ester 1b was subjected to cyclopropanation with diethyl zinc, trifluoroacetic acid and diiodomethane which gave the known cyclopropyl-bis-boronic ester 9 29 followed by a Suzuki coupling reaction with 5-(bromoethynyl)-1,2,3-trimethoxybenzene (Scheme 4).…”

Site-Selective Functionalization of C(sp3) Vicinal Boronic Esters

“…The products were obtained in good yield and with exquisite selectivity, leaving the other boryl moiety intact. An alternative and recent approach to racemic cyclopropyl-1,2-bis(boronates) has been reported by the Ghosh and Berreé group, 19 using a Simmons−Smith cyclopropanation of alkenyl-1,2-bis(boronates). The resulting cyclopropanes (Scheme 12b), which contain both secondary and tertiary boronic esters, render regioselective Suzuki−Miyaura cross-coupling at the secondary position.…”