Two-Phase Dibromocyclopropanation of Unsaturated Alcohols Using Flow Chemistry

Abstract

Dibromocyclopropanations are conventionally done by addition of dibromocarbene to alkenes under phase-transfer conditions in batch reactions using a strong base (50% NaOH (aq)), vigorous stirring and long reaction times. We have shown that cyclopropanation of unsaturated alcohols can be done under ambient conditions using continuous flow chemistry with 40% (w/w) NaOH (aq) as the base. The reactions were generally rapid; the yields were comparable to yields reported in the literature for the conventional batch reaction

Interfacial Processes—The Key Steps of Phase Transfer Catalyzed Reactions

“…Turbulent flow assures particularly large interfacial surface. This technique was successfully applied for a few reactions that proceed without a PT catalyst, and also PT catalyzed reactions, particularly for generation and reactions of dibromo- [43,44] and dichlorocarbenes [45] (Scheme 22).…”

“…An important factor that affects efficiency of the PTC reactions of carbanions in the liquid-liquid two-phase systems is effect of the structure of the TAA cations on rate of the interfacial ion exchange and transfer of the formed lipophilic ion pairs from the interface into the bulk of the organic phase. This very complicated problem was studied and thoroughly discussed by Denmark [44].…”

A DFT Study on the Molecular Mechanism of Additions of Electrophilic and Nucleophilic Carbenes to Non-Enolizable Cycloaliphatic Thioketones

“…Great importance of both electrophilic and nucleophilic carbenes, in the current organic and organometallic chemistry, is demonstrated by a large number of original publications and reviews, which have appeared in the last five years [8][9][10][11][12]. Very recently, new reactions within situ generated carbenes, using non-conventional techniques, such as mechanochemical synthesis [13] or flow-technique [14], have also been reported.…”