Selective Electrochemical Dibromination of Terpenes and Naturally Derived Olefins

Abstract

A simple electrochemical protocol is established for the selective alkene dibromination of naturally derived olefins, such as terpenes. The use of hazardous Br 2 or its analogues have been elegantly avoided by employing readily available, inexpensive, and harmless sodium bromide with a dual role as reagent and supporting electrolyte in combination with sustainable carbon-based electrodes. This electrochemical protocol provides the desired products with good to excellent yields up to 82 % with 10 examples. Scalability has been proved by a 5fold scale-up. Notably, higher yields and selectivity were achieved in comparison to conventional bromination by Br 2 and DMSO/HBr system and the dibrominated compound was eligible for further functionalization, such as cyanation according to the Kolbe nitrile synthesis protocol.

Dual Roles of Supporting Electrolytes in Organic Electrosynthesis

“…[35] up to 82 %. [33] This electrochemical approach proved to be superior in selectivity towards conventional methods.…”

“…a Dibromination of naturally occurring alkenes with sodium bromide. [33] b Bromination of different aromatics using tetrabutylammonium bromide. [34] c Bromo cyclization using magnesium bromide.…”

“…The selective dibromination of delicate terpenes and naturally derived olefines using simple sodium bromide as a supporting electrolyte and bromination agent was described in our group (Scheme 8a). Upon oxidation of the bromide anions to form a bromine/tribromide equilibrium, the bromine reacts with the alkene double bond to form the dibrominated species yielding up to 82 % [33] . This electrochemical approach proved to be superior in selectivity towards conventional methods.…”

Seminormal-BrCH2CH2OH-mediated electrochemical epoxidation of unactivated olefins

“…The low concentration of Br − is anodized to regenerate Br 2 to allow the reaction to proceed smoothly under seminormal bromine source conditions and effectively avoid the dibromination of olefins. 21…”

Electrifying synthesis of organosilicon compounds – from electrosynthesis to electrocatalysis

“…Looking at organic chemistry we notice a tremendous growth of interest in the development of novel electrochemical methodologies. Ackermann, [1][2][3][4] Baran, [5][6][7][8] Lin, 9,10 Mei, [11][12][13] Waldvogel [14][15][16] and many other eminent scientists have proverbially brought electrosynthesis/electrocatalysis to light by turning it into a perfectly working synthetic tool. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] This, in turn, has many implications for the development of materials chemistry.…”