Hydrogen bond donor–acceptor–donor organocatalysis for conjugate addition of benzylidene barbiturates via complementary DAD–ADA hydrogen bonding

Organocatalysts featuring a hydrogen bond donor–acceptor–donor structural element catalyze conjugate addition via complementary DAD–ADA hydrogen bonding.

Regioselective template synthesis, X-ray structure, and chiroptical properties of a topologically chiral sulfonamide catenane

The synthesis of a topologically chiral in,out-bis-sulfonamide catenane and its "dimer" are reported. The structures of the amide wheel and of the catenane were resolved by X-ray analysis. NMR-titration of the monosulfonamide-wheel yielded conclusive association constants supporting the proposed regioselective mechanism of the catenane formation. The enantioseparation of the catenane via chiral HPLC was successful. The enantiomers show pronounced Cotton effects in the aromatic region of the CD-spectrum. Since the template synthesis was carried out leading to the in-oriented sulfonamide-wheel blocked with an N-methyl group at its reactive sulfonamide functionality, the catenane represents the first monofunctional topologically chiral amide-based catenane. Reaction with 1,2-bis(2-iodoethoxy)ethane led to a bis-catenane containing two topological units. The meso- and the RR/SS-isomers represent a new type of topological diastereomers.