sp³C–H activationvia exo-type directing groups

Abstract

The application of exo-type directing groups (DGs) has led to the discovery of a wide range of novel C(sp3)–H activation methods, which allow efficient and site-selective functionalization of alcohol and amide derivatives.

Weakly-coordinating N-oxide and carbonyl groups for metal-catalyzed C–H activation: the case of A-ring functionalization

“…C-H activations assisted by this sort of DGs have been widely studied. 12 The diverse viable functional groups used as DGs include amides, amines, anilines, heterocyclic compounds, carboxylic acids, N-oxide and carbonyl groups. 13 Among these DGs, the use of weakly-coordinating directing groups 14 emerged as particularly important in order to expand the scope of the previously unavailable substrates.…”

Palladium(II)‐Catalyzed Enantioselective Arylation of Unbiased Methylene C(sp3)−H Bonds Enabled by a 2‐Pyridinylisopropyl Auxiliary and Chiral Phosphoric Acids

“…In the pre‐transition‐state intermediate C , the chiral phosphoric amide is relatively free to rotate (Scheme c), which could result in different chiral environments with opposite stereoinduction and erode the enantioselectivity. Considering the vast number of aliphatic C−H functionalization reactions that are enabled by bidentate directing groups,– the identification of chiral ligands for highly stereoselective C−H activation reactions of unbiased aliphatic C−H bonds with bidentate auxiliaries would be highly desirable.…”

[1,5]-Hydride Shift-Cyclization versus C(sp2)-H Functionalization in the Knoevenagel-Cyclization Domino Reactions of 1,4- and 1,5-Benzoxazepines

“…C-H activation and functionalization of sp 3 -and sp 2 -hybridized carbons offer atom-economical and step-efficient ways for the preparation of polyfunctionalized condensed heterocycles, which have In this work, the N-aryl-1,5-benzoxazepine derivative 4 was converted to the carbocationic intermediate 5 with 1,3-dimethylbarbituric acid in a Knoevenagel reaction, which cyclized with the activated benzene ring to produce a condensed 9,10-dihydroacridine (acridane) derivative 6 in an S E Ar reaction. The different position of the nitrogen atom in the benzoxazepine scaffold induced a sequence different from those depicted in Scheme 1b for the regioisomeric rac-1; a C(sp 2 )-H functionalization took place instead of the [1,5]-hydride shift-cyclization, which was observed for N-aryl-1,4-benzoxazepines. The transformation of 4 to 6 involves the activation of the carbonyl carbon during the Knoevenagel reaction and a C(sp 2 )-H functionalization during the S E Ar reaction.…”