Synthesis and Applications of 1,1-Diborylated Cyclopropanes: Facile Route to 1,2-Diboryl-3-methylenecyclopentenes

Abstract

Cyclopropylidene lithium carbenoids reacted with bis(pinacolato)diboron in THF/Et2O at −110 °C to give various 1,1-diborylated cyclopropanes in good yields. Treatment of the diborylated cyclopropanes with 3-chloro-1-lithio-3-methyl-1-butyne produced the corresponding diborylated allenylcyclopropanes, which underwent ring-expansion in the presence of a Rh catalyst to give 1,2-diborylated methylenecyclopentenes conveniently.

Selective Boryl‐Anion Migration in a Vinyl sp2−sp3 Diborane Induced by Soft Borane Lewis Acids

“…[11][12][13][14][15][16][17] We hypothesised that an alternative route to induce intramolecular 1,2-boryl-anion migration would be the activation of an unsaturated R À group (e.g. [11][12][13][14][15][16][17] We hypothesised that an alternative route to induce intramolecular 1,2-boryl-anion migration would be the activation of an unsaturated R À group (e.g.…”

Simple Access to Elusive α-Boryl Carbanions and Their Alkylation: An Umpolung Construction for Organic Synthesis

“…While some alkylations required slightly elevated reaction temperatures, it is remarkable that construction of highly hindered reaction product 20 could proceed effectively at rt. Also of note, geminal bis(boryl)cyclopropanes, readily available from borylation of the corresponding 1,1-dibromocyclopropane, 20 could be alkylated with good yield and with outstanding levels of stereocontrol (compounds 22 and 23 ).…”

Synthesis of Multisubstituted Olefins through Regio‐ and Stereoselective Addition of Interelement Compounds Having B–Si, B–B, and Cl–S Bonds to Alkynes, and Subsequent Cross‐Couplings

“…The intermediate 16b was treated with pinacol in the presence of NaHCO 3 to generate the gem ‐diborylated olefin 17 ,95 whose spectroscopic data were identical to those of an authentic sample 69,96. The gem ‐diborylated olefins are recognized as useful building blocks for functional materials and natural products, as well as bioactive pharmaceuticals 97,98…”