Enantioselective Radical Construction of 5-Membered Cyclic Sulfonamides by Metalloradical C-H Amination.

Both arylsulfonyl and alkylsulfonyl azides can be effectively activated by the cobalt(II) complexes of D2-symmetric chiral amidoporphyrins for enantioselective radical 1,5-C-H amination to stereoselectively construct 5-membered cyclic sulfonamides. In addition to C-H bonds with varied electronic properties, the Co(II)-based metalloradical system features chemoselective amination of allylic C-H bonds and is compatible with heteroaryl groups, producing functionalized 5-membered chiral cyclic sulfonamides in high yields with high enantioselectivities. The unique profile of reactivity and selectivity of the Co(II)-catalyzed C-H amination is attributed to its underlying stepwise radical mechanism, which is supported by several lines of experimental evidence.

Cobalt carbaporphyrin-catalyzed cyclopropanation.

Cobalt complexes of N-confused porphyrins and benziphthalocyanine, which both feature organometallic bonds at the macrocycle cores, catalyze the cyclopropanation of styrene with a higher trans-selectivity than the corresponding porphyrin and phthalocyanine complexes.

Synthesis of diporphyrins via palladium-catalyzed C-O bond formation: effective access to chiral diporphyrins.

Diporphyrins can be efficiently synthesized from bromoporphyrin precursors via palladium-catalyzed C-O bond formation. The synthetic methodology is general and can be applied to various diols, forming a series of homo-diporphyrins containing different types of spacers in high to excellent yields. Chiral diporphyrins can be readily constructed through the use of optically active diols. A similar strategy allows access to hetero-diporphyrins and triporphyrins, including free-base and metalloporphyrin hetero dimers.

Bromoporphyrins as versatile synthons for modular construction of chiral porphyrins: cobalt-catalyzed highly enantioselective and diastereoselective cyclopropanation.

5,10-Bis(2',6'-dibromophenyl)porphyrins bearing various substituents at the 10 and 20 positions were demonstrated to be versatile synthons for modular construction of chiral porphyrins via palladium-catalyzed amidation reactions with chiral amides. The quadruple carbon-nitrogen bond formation reactions were accomplished in high yields with different chiral amide building blocks under mild conditions, forming a family of D2-symmetric chiral porphyrins. Cobalt(II) complexes of these chiral porphyrins were prepared in high yields and shown to be active catalysts for highly enantioselective and diastereoselective cyclopropanation under a practical one-pot protocol (alkenes as limiting reagents and no slow addition of diazo reagents).