Free-Radical Carboalkynylation and Carboalkenylation of Olefins

Abstract

Free-radical three-component carboalkynylation and -alkenylation of olefins have been developed. These involve the addition, across the double bond of an unactivated olefin, of a radical species α- to an electron-withdrawing group and an alkenyl or alkynyl moiety, derived from the corresponding sulfones.

Free‐Radical Carbocyanation of Olefins

“…For large‐scale synthesis and for costly olefins, the use of 2 equiv of olefin (Table , entries 2 and 4) generally gave acceptable yields. As already observed before,, electron‐rich olefins (enol ethers, enamides, allylsilanes, etc.) are more reactive, and 2 equiv are usually sufficient to attain reasonable yields.…”

“…Moreover, the presence of the reactive orthogonal thioester group allows for further manipulation in the presence of esters, as in 6 d . As observed in carbo‐alkenylation and carbo‐oximation reactions,,, electron‐richer olefins reacted faster and led to higher yields, as illustrated by the formation of silane 6 i or ether 6 j . In contrast with the carbo‐oximation reaction, which led to moderate yields with sterically hindered substrates, carbocyanation allowed the incorporation of the cyano group on tertiary centers and thus the generation of all‐carbon quaternary centers as in 6 a – f .…”

“…On the basis of previous work on carbo‐azidation, carbo‐alkenylation,, and carbo‐oximation,, we describe herein an efficient three‐component free‐radical carbocyanation of electron‐rich olefins . Optimization of the process also led us to develop a tin‐free (two‐component) version of this carbocyanation using a readily available sulfonyl cyanide incorporating both functional groups to be added to the olefin.…”

Strongly Luminous Tetranuclear Gold(I) Complexes Supported by Tetraphosphine Ligands, meso‐ or rac‐Bis[(diphenylphosphinomethyl)phenylphosphino]methane

“…Landais et al38 described the synthesis of γ‐alkynyl esters (Scheme ) by means of an efficient cascade reaction involving the addition of free radicals (generated in situ) to olefins and the subsequent capture of the resulting radicals by the corresponding alkynyl sulfones. Moderate to good yields of γ‐alkynyl esters were obtained by use of different xanthates and DTBHN as radical initiator.…”

Radical electrophilicities in solvent

“…This scale, based on the electrophilicity index as introduced by Parr et al [2] (for a recent review see Chattaraj et al [3]) and defined as the electronic chemical potential squared over two times the chemical hardness, has proven its value since assisting in classifying radical systems [4][5][6][7][8][9][10], explaining reaction behavior and introducing other chemical concepts like radical stability [11][12][13][14]. The question arises, though, as to whether the order of this gas-phase electrophilicity scale still holds for radicals in solution.…”