Cyclopropanation ofN-vinylimidesviaa redox-neutral photocatalysed radical addition/anionic cyclisation process

Abstract

Radical addition/SET reduction/3-exo-tert cyclisation process has emerged as a useful and powerful strategy for the preparation of functionalized cyclopropanes. Herein, a novel protocol dealing with the preparation of cyclopropylamines has...

Photoredox-catalyzed radical–radical cross coupling of ketyl radicals with unstabilized primary alkyl radicals

“…Interestingly, in contrast to the cyclopropanation of β-phthaliminoacrylate methyl ester 6 with halomethylsilicates, 14 the expected radical–radical cross coupling reaction between 6 and ethylsilicate 2a was observed, affording 7a in 67% yield. Moreover, the structure of adduct product 7b derived from the reaction of 6 with iso-butylsilicate was unambiguously determined via X-ray crystallography (Scheme 3).…”

3-Chloropropylbis(catecholato)silicate as a Bifunctional Reagent for the One-Pot Synthesis of Tetrahydroquinolines from o-Bromosulfonamides

“…As part of our efforts to develop reagents for photoredox-enabled carbocycle and heterocycle synthesis, we became intrigued by the possibility of developing a bifunctional reagent capable of sequential, one-pot cross-coupling and nucleophilic substitution reactions. Bis­(catecholato)­silicate salts are well suited for such a purpose. , These reagents, which are easily prepared from inexpensive trialkoxysilanes, have low oxidation potentials (approximately +0.75 V vs SCE) and can readily furnish primary alkyl radical equivalents under photoredox catalysis. Importantly, these organosilicates can be adorned with a variety of pendant functional groups, including halogens.…”

“…Thus, these organosilicate salts have great potential as bifunctional reagents: the organosilicate and halide ends can operate independently of one another in radical and polar reactions, respectively (Scheme ). This feature of the reagents has been leveraged in the past for pyrrolidine formation and the synthesis of several types of substituted cyclopropanes using a net-neutral radical/polar crossover mechanism …”

“…As part of our efforts to develop reagents for photoredox-enabled carbocycle and heterocycle synthesis, 13 we became intrigued by the possibility of developing a bifunctional reagent 14 capable of sequential, one-pot cross-coupling and nucleophilic substitution reactions. Bis(catecholato)silicate salts are well suited for such a purpose.…”

Unprecedented single-electron-transfer reduction-based N → C acyl migration reactions of imides enabled by redox-neutral photocatalysis

“…The carbanion neighbor to the imide nitrogen was proposed as the key intermediate for migration transformation. Recently, we successfully realized the redox-neutral-photocatalyzed CH 2 transfer reactions 8 of N -vinylimides with halomethylsilicate 9 via a radical addition/SET reduction/3- exo-tet cyclization cascade process (Scheme 2b, path I). 10 Inspired by this reductive RPC-based cyclopropanation reaction, we proposed that the acyl migration reaction would take place due to the appropriate formation of an α-imido carbanion derived from SET reduction of an adduct radical generated from the radical addition of N -vinylimides with alkyl radicals instead of halomethyl radicals (Scheme 2b, path II).…”