Metal-free Mizoroki–Heck type reaction: a radical oxidative coupling reaction of 2-chloro-dithiane with substituted olefins

Abstract

An efficient metal-free Mizoroki-Heck type reaction of di- and tri-substituted alkenes with 2-chloro-dithiane has been developed under ambient pressure of air or using a relatively low loading of BF3·Et2O. This study represents a new environmentally friendly method for the syntheses of dithianyl-substituted alkene derivatives via a radical oxidative coupling process.

Sunlight‐Driven Synthesis of Triarylethylenes (TAEs) via Metal‐Free Mizoroki–Heck‐Type Coupling

“…As hinted above, the development of a metal‐free Mirozoki–Heck coupling has been documented in literature and such protocols were sometimes applied to the building of a triarylethylene core , . However, whereas the previous examples showed a limited scope, the present proposal can be efficiently applied to a wide range of substrates (including heteroaromatics), with the only exception of compounds bearing strong electron‐donating substituents such as 2m (which already gave unsatisfactory results in previous investigations) …”

“…Another strategy relies on the formation of an Aryl–Csp 2 bond and, among the different approaches proposed, the Mizoroki–Heck reaction involving the coupling of a 1,2‐ (path c), [15a], [15b] or a 1,1‐ (path d)[15a], [15c] disubstituted alkene with an aryl halide is the most attractive since no previous activation of the olefin is needed. Recently several efforts have been devoted to improve the Heck reaction in terms of sustainability and safety, but only little attention has been given to the development of metal‐free protocols, most of them exploiting photochemical conditions . However, despite the formation of a triarylethylene from 1,1‐diphenylethylene and aryl halides (iodides, chlorides) has been described to occur via the photogeneration of a triplet aryl cation (path e) or an aryl radical (path f), the scope of such proposals is rather limited, and, a high energy demanding UV‐light source is required to activate the aromatic substrates , .…”

Access to Electron-Deficient 2,2-Disubstituted Chromanes: A Highly Regioselective One-Pot Synthesis via an Inverse-Electron-Demand [4 + 2] Cycloaddition of ortho-Quinone Methides

“…Unless otherwise noted, commercially purchased reagents were used as received. 1,1-Disubstituted ethylenes were prepared according to published methods. − …”

Di‐tert‐Butyl Peroxide‐Mediated Atom‐Transfer Radical Addition of 2‐Chlorodithiane to Aryl Alkynes under Mild Conditions

“…In our recent work on radical oxidative coupling, we reported a general method for the proposed ATRA of 2‐chlorodithiane and arylalkenes in the presence of an iron catalyst system;8a toward the further study, we discovered that O 2 is also a highly effective oxidant for dithiane radical oxidative couplings 8b. Based on these findings, we attempted to apply a similar oxidation system or metal catalyst to the coupling of phenylacetylene 1 a and 2‐chlorodithiane 2 .…”