Hydroalkylation of Unactivated Olefins via Visible-Light-Driven Dual Hydrogen Atom Transfer Catalysis

Abstract

Radical hydroalkylation of olefins enabled by hydrogen atom transfer (HAT) catalysis represents a straightforward means to access C­(sp 3)-rich molecules from abundant feedstock chemicals without the need for prefunctionalization. While Giese-type hydroalkylation of activated olefins initiated by HAT of hydridic carbon–hydrogen bonds is well-precedented, hydroalkylation of unactivated olefins in a similar fashion remains elusive, primarily owing to a lack of general methods to overcome the inherent polarity-mismatch in this scenario. Here, we report the use of visible-light-driven dual HAT catalysis to achieve this goal, where catalytic amounts of an amine-borane and an in situ generated thiol were utilized as the hydrogen atom abstractor and donor, respectively. The reaction is completely atom-economical and exhibits a broad scope. Experimental and computational studies support the proposed mechanism and suggest that hydrogen-bonding between the amine-borane and substrates is beneficial to improving the reaction efficiency.

Visible-light mediated catalytic asymmetric radical deuteration at non-benzylic positions

“…During our investigations on photoinduced hydroalkylation of olefins under the joint catalysis of Lewis base-borane and thiol 42 , we serendipitously observed the addition of N-heterocyclic carbene (NHC)-BH 3 complex 43,44 1a onto olefins. While photoinduced hydroboration of olefins using NHC-BH 3 complexes have been disclosed recently by several groups [45][46][47][48][49] , asymmetric version of the reaction remains unexplored.…”

α-Branched amines through radical coupling with 2-azaallyl anions, redox active esters and alkenes

“…Before initiating our investigation, reaction conditions used in 2-azaallyl coupling reactions, 19,42 alkene functionalization reactions 75,76 and reductive activation of RAEs 60,77–82 were studied. Based on these works, Ni(COD) 2 was selected as the metal source, 33 DIPEA as base, 31,59,69,83 THF/DMF as solvent (4 : 1, based on literature precedence 50,51,84 ).…”

Organophotocatalytic Regioselective C−H Alkylation of Electron‐Rich Arenes Using Activated and Unactivated Alkenes

“…Vinyl borates could be transformed into β‐arylated alkyl borates ( 5 m ) in 84 % yield. Notably, unactivated alkenes could undergo the C−H hydroalkylation of arenes to deliver corresponding products ( 5 n – 5 q , 5 t , 5 x , 5 y ), which is complementary to C−H hydroalkylation of activated alkanes [26] . 1,1‐Disubstituted terminal aliphatic alkenes with diverse functional groups, such as esters, ethers, amides with free N−H, were also compatible in this reaction, delivering the desired C−H alkylation products ( 5 n – 5 q ) in 54–76 % yields.…”

“…Notably, unactivated alkenes could undergo the CÀ H hydroalkylation of arenes to deliver corresponding products (5 n-5 q, 5 t, 5 x, 5 y), which is complementary to CÀ H hydroalkylation of activated alkanes. [26] 1,1-Disubstituted terminal aliphatic alkenes with diverse functional groups, such as esters, ethers, amides with free NÀ H, were also compatible in this reaction, delivering the desired CÀ H alkylation products (5 n-5 q) in 54-76 % yields. Moreover, internal aliphatic alkenes are all good substrates for this reaction, which substantially expanded the scope of this CÀ H alkylation reaction.…”