Remote Allylation of Unactivated C(sp³)–H Bonds Triggered by Photogenerated Amidyl Radicals

Abstract

The allylation reaction is a highly versatile transformation in chemical synthesis. While many elegant direct C­(sp2)–H allylation reactions have been developed, the direct allylation of unactivated C­(sp3)–H bonds is underdeveloped. By applying photoredox catalysis and a [1,5]-HAT process, herein we report a direct allylation of unactivated C­(sp3)–H bonds. This photocatalyzed transformation is tolerant of several functional groups in the amide and allylic chloride substrates. Various allyl-substituted amide products were obtained with good yields and high δ-selectivity.

Enantiocomplementary C–H Bond Hydroxylation Combining Photo‐Catalysis and Whole‐Cell Biocatalysis in a One‐Pot Cascade Process

“…Carbonyl reductase from Kluyveromyces thermotolerans (KtCR) was chosen as a model enzyme which was identified with satisfactory R-selectivity. [16] Initially, we performed the cascade reaction with all factors in one-pot. Unfortunately, the process was ineffective, only 5 % desired chiral product (3a) was observed.…”

Site-selective remote C(sp3)–H heteroarylation of amides via organic photoredox catalysis

“…This strategy offers a marvelous pathway to selectively achieve mild C–H bond cleavage and C–X (X = halides) and C–N bond formation 19 . Furthermore, interrupted HLF reactions using electron-deficient alkenes 23–27 , vinyl boronic acids 28,29 , allyl sulfones 30 , allylic chlorides 31 , etc. 32,33 as carbon-centered radical traps open a new window for remote C(sp 3 )–C bond formation.…”

An Update on Distal C(sp3)−H Functionalization Involving 1,5‐HAT Emerging from Nitrogen Radicals

“…In contrast with iridium photocatalyst they have used Ni(COD) 2 as a cheaper source and bidentate ligands to increase the efficiency of formation of the product (Scheme 10a). [31] Control experiment suggests the presence of Ni-catalyst and a suitable ligand is not necessary for the allylation to take place. Later on in this year Rovis reported another dual catalytic method for distal alkylation of unactivated aliphatic amides using photocatalyst [Ir(dF(CF 3 ) ppy) 2 (dtbbpy)]PF 6 and Ni(glyme)Cl 2 (Scheme 10b).…”

“…Another probable protocol is established by Tambar's group for δ‐C−H allylation of unactivated aliphatic units by 1,5‐HAT process to generate C ‐centered radical from an amidyl radical. In contrast with iridium photocatalyst they have used Ni(COD) 2 as a cheaper source and bidentate ligands to increase the efficiency of formation of the product (Scheme a) . Control experiment suggests the presence of Ni‐catalyst and a suitable ligand is not necessary for the allylation to take place.…”