Alkene Carboarylation through Catalyst‐Free, Visible Light‐Mediated Smiles Rearrangement

Abstract

A light‐mediated Truce–Smiles arylative rearrangement is described that proceeds in the absence of any photocatalyst. The protocol creates two C−C bonds from simple starting materials, with the installation of an aryl ring and a difluoroacetate moiety across unactivated alkenes. The reaction proceeds via a radical mechanism, utilizing a light‐mediated reduction of ethyl bromodifluoroacetate by N,N,N′,N′‐tetramethylethylenediamine (TMEDA) to set up intermolecular addition to an unactivated alkene, followed by Truce–Smiles rearrangement.

Truce–Smiles Rearrangements by Strain Release: Harnessing Primary Alkyl Radicals for Metal‐Free Arylation

“…see SI for details). The background reactivity observed when the substrate was irradiated in the absence of catalyst could be attributed to potential electron‐donor acceptor (EDA) complex reactivity, something that we, and others, have previously reported as an effective strategy for Truce–Smiles rearrangements [2e, 9b, 10] …”

Photocatalyzed cycloaromatization of vinylsilanes with arylsulfonylazides

“…However, the modes of radical Smiles rearrangement are very limited. Up to now, only α-carbonyl radical 26 – 30 , β-aminoalkyl radical 31 – 33 , N -centered radical 34 , and ketyl radical 35 - triggered Smiles rearrangement have been exploited to construct nitrogen-heterocycles, and vinylsilane-based Smiles rearrangement keep unexplored. As is well known, vinylsilanes have proven to be important “alkene” sources in Hiyama coupling, which could efficiently incorporate C=C bond in a particular molecule with the release of silyl moiety 36 ; Meanwhile, the high electronegativity of carbon (2.35) relative to silicon (1.64) 37 and silyl-hyperconjugation effect (the so-called β-effect) 38 – 40 generally endow these compounds with the versatile reactivity.…”

Promising reagents for difluoroalkylation

“…was described by the group of Duong and Greaney (Scheme 18). 74 This transformation simultaneously introduced an aryl ring and a difluoroacetate moiety across unactivated alkenes. A radical mechanism was proposed for this reaction.…”