Aerobic cross-dehydrogenative couplings of N-heteroarenes with toluene derivatives at room temperature

Abstract

A mild aerobic cross-dehydrogenative coupling between N-heteroarenes and benzylic C(sp3)-H bond has been achieved through the visible-light-induced photocatalysis. This approach provides a sustainable alternative to Minisci benzylation reactions with readily...

Alkylation/Ipso-cyclization of Active Alkynes Leading to 3-Alkylated Aza- and Oxa-spiro[4,5]-trienones

“…Green development has always been an eternal topic in the field of chemistry. − The radical reactions, a class of new and developing reactions, have received extensive attention of chemists because of their mild conditions, rapid reactions, and diverse reaction forms. , Combining the requirements of green development and our interest in radical reactions, we develop a transition-metal-free alkylation/ipso-cyclization of activated alkynes with 4-alkyl-1,4-dihydropyridines for the preparation of 3-alkylated aza - and oxa -spiro­[4,5]-trienones, in which H 2 O provides an oxygen atom for the construction of the newly generated carbonyl group (Scheme ).…”

Stoichiometric couplings of methylarenes through visible-light-induced bromo radical formation from aryl halides

“…Based on the above described mechanism studies and previous reports, 11,17,23 a detailed description of our proposed mechanism cycle for the direct arylation of benzylic C(sp) 3 –H bonds through photoredox HAT–nickel dual catalysis is shown in Scheme 3. The Ni II aryl bromide intermediate C was furnished via the oxidative addition of Ni(0) complex B to aryl bromide 2 .…”

“…8 However, in our previous report, we found that a bromine radical could activate the benzylic C–H bonds. 11 On this basis, we examined the direct arylation in the presence of 4-bromobenzonitrile ( 1a ), 1-methoxy-4-methylbenzene ( 2a , 10 equiv. ), [Ir(dF(CF 3 )ppy) 2 (dtbpy)]PF 6 ( PC1 ), NH 4 Br, Ni(acac) 2 , dtbbpy ( L1 ) and K 2 HPO 4 in acetone, which delivered 1,1-diaryl alkanes 3a in 92% yield (Table 1, entry 2).…”

“…Recently, we have developed the aerobic cross-dehydrogenative coupling of N-heteroarenes with toluene derivatives and proved that the bromine radical could activate benzylic C-H bonds via hydrogen atom transfer (HAT). 11 Bromine radicals have also been proved by others as efficient and powerful hydrogen atom abstraction reagents in C-H bond activation, such as in the α-heterosubstituted C(sp) 3 -H bond, 12 benzylic C(sp) 3 -H bond, 13 allylic C(sp) 3 -H bond, 14 α-amino C(sp) 3 -H bond, 15 unactivated alkene C(sp) 3 -H bond 16 and aldehyde C(sp) 2 -H bond. 17 Therefore, we envisaged that this theory of the bromine radical for hydrogen atom abstraction, which was in situ generated by photocatalysis, could be further extended to stoichiometric couplings of various benzylic C-H bonds.…”

Photocatalytic cross-dehydrogenative coupling reaction toward the synthesis of N,N-disubstituted hydrazides and their bromides

“…The cross-dehydrogenative coupling (CDC) reaction between two readily available chemical entities has emerged as an important and straightforward synthetic strategy for C–N bond formation, whereby the only byproduct is H 2 formally. 35 On the other hand, photocatalytic organic synthesis is a continuous hot topic using visible light as green energy under environmentally friendly conditions. 36,37 In particular, visible light catalyzed/promoted cross-dehydrogenative coupling reactions represent a powerful C–N bond formation platform to produce various nitrogen-containing fine chemicals.…”