Auxiliary-Enabled Pd-Catalyzed Direct Arylation of Methylene C(sp3)–H Bond of Cyclopropanes: Highly Diastereoselective Assembling of Di- and Trisubstituted Cyclopropanecarboxamides

Enantioselective palladium(0)-catalyzed intramolecular cyclopropane functionalization: access to dihydroquinolones, dihydroisoquinolones and the BMS-791325 ring system

Taddol-based phosphoramidite ligands enable enantioselective palladium(0)-catalyzed C-H arylation of cyclopropanes. The cyclized products are obtained in high yields and enantioselectivities. The reported method provides efficient access to a broad range of synthetically attractive cyclopropyl containing dihydroquinolones and dihydroisoquinolones as well as allows for an efficient enantioselective construction of the 7-membered ring of the cyclopropyl indolobenzazepine core of BMS-791325.

Chiral γ-Lactams by Enantioselective Palladium(0)-Catalyzed Cyclopropane Functionalizations

Cyclopropanes fused to pyrrolidines are important structural features found in a number of marketed drugs and development candidates. Typically, their synthesis involves the cyclopropanation of a dihydropyrrole precursor. Reported herein is a complementary approach which employs a palladium(0)-catalyzed C-H functionalization of an achiral cyclopropane to close the pyrrolidine ring in an enantioselective manner. In contrast to aryl-aryl couplings, palladium(0)-catalyzed C-H functionalizations involving the formation of C(sp(3) )-C(sp(3) ) bonds of saturated heterocycles are very scarce. The presented strategy yields cyclopropane-fused γ-lactams from chloroacetamide substrates. A bulky Taddol phosphonite ligand in combination with adamantane-1-carboxylic acid as a cocatalyst provides the γ-lactams in excellent yields and enantioselectivities.

Asymmetric C-H functionalization of cyclopropanes using an isoleucine-NH2 bidentate directing group

The systematic investigation of substrate-bound α-amino acid auxiliaries has resulted in catalytic asymmetric C-H functionalization of cyclopropanes enabled by amino acid amides as chiral bidentate directing groups. The use of an Ile-NH2 auxiliary embedded in the substrate provided excellent levels of asymmetric induction (diastereomeric ratio of up to 72 : 1) in the Pd(ii)-catalyzed β-methylene C(sp3)-H bond activation of cyclopropanes and cross-coupling with aryl iodides.

Nickel-catalyzed synthesis of diarylsulfides and sulfones via C–H bond functionalization of arylamides

The sulfenylation and sulfonylation of (sp²)C–H bonds of benzamides were achieved with the aid of a bidentate directing group.

Pd-catalyzed α-selective C(sp3)–H acetoxylation of amides through an unusual cyclopalladation mechanism

A novel Pd-catalyzed site-selective α-C(sp³)–H oxidation/acetoxylation of amides through an unusual [4,6]-bicyclic metallacycle intermediate was reported with 1-aminoanthraquinone as a new BDG.

Applications of C-H functionalization logic to cyclobutane synthesis

The application of C-H functionalization logic to target-oriented synthesis provides an exciting new venue for the development of new and useful strategies in organic chemistry. In this article, C-H functionalization reactions are explored as an alternative approach to access pseudodimeric cyclobutane natural products, such as the dictazole and the piperarborenine families. The use of these strategies in a variety of complex settings highlights the subtle geometric, steric, and electronic effects at play in the auxiliary guided C-H functionalization of cyclobutanes.

Nickel-catalyzed direct arylation of C(sp3)-H bonds in aliphatic amides via bidentate-chelation assistance

The Ni-catalyzed, direct arylation of C(sp(3))-H (methyl and methylene) bonds in aliphatic amides containing an 8-aminoquinoline moiety as a bidentate directing group with aryl halides is described. Deuterium-labeling experiments indicate that the C-H bond cleavage step is fast and reversible. Various nickel complexes including both Ni(II) and Ni(0) show a high catalytic activity. The results of a series of mechanistic experiments indicate that the catalytic reaction does not proceed through a Ni(0)/Ni(II) catalytic cycle, but probably through a Ni(II)/Ni(IV) catalytic cycle.

Catalytic functionalization of C(sp2)-H and C(sp3)-H bonds by using bidentate directing groups

C-H bonds are ubiquitous in organic compounds. It would, therefore, appear that direct functionalization of substrates by activation of C-H bonds would eliminate the multiple steps and limitations associated with the preparation of functionalized starting materials. Regioselectivity is an important issue because organic molecules can contain a wide variety of C-H bonds. The use of a directing group can largely overcome the issue of regiocontrol by allowing the catalyst to come into proximity with the targeted C-H bonds. A wide variety of functional groups have been evaluated for use as directing groups in the transformation of C-H bonds. In 2005, Daugulis reported the arylation of unactivated C(sp(3))-H bonds by using 8-aminoquinoline and picolinamide as bidentate directing groups, with Pd(OAc)2 as the catalyst. Encouraged by these promising results, a number of transformations of C-H bonds have since been developed by using systems based on bidentate directing groups. In this Review, recent advances in this area are discussed.