Funktionalisierung von C-H-Bindungen: neue Synthesemethoden für Naturstoffe und Pharmazeutika

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.

C-H alkenylation of azoles with enols and esters by nickel catalysis

Rather u(Ni)que: Two new C-H alkenylation reactions, that is C-H/C-O alkenylation and decarbonylative C-H alkenylation, of azoles are uniquely catalyzed by Ni/dcype. These azole alkenylation reactions are successfully applied to the convergent formal synthesis of siphonazole B.

Enantioselective C-H arylation strategy for functionalized dibenzazepinones with quaternary stereocenters

Tada! Highly functionalized chiral dibenzazepinones are obtained by a mild palladium(0)-catalyzed enantioselective C-H arylation with excellent selectivities by using simple taddol phosphoramidite ligands. The amide tether allows exclusive regioselectivity through a rare eight-membered palladacycle intermediate.

Synthesis of Phenanthridinones from N-methoxybenzamides and aryltriethoxysilanes through Rh(III)-catalyzed C-H and N-H bond activation

An efficient method for the one-pot synthesis of substituted phenanthridinone derivatives from N-methoxybenzamides and aryltriethoxysilanes through rhodium-catalyzed dual C-H bond activation and annulation reactions is described. A double-cycle mechanism is proposed to account for this catalytic reaction. In addition, isotope-labeling studies were performed to understand the intimate mechanism of the reaction.