2006

ABSTRACT:

A Mannich–aza-Michael reaction in which both an electrophile and a nucleophile are activated provides a simple, highly enantioselective route to isoquinuclidines (1) from imines (2) and cyclohexenone (3). A feature of the reaction is the interplay of an achiral and a chiral Brønsted acid, which enable the asymmetric reaction process by cooperative activation of the enone and the imine.

ABSTRACT:

The hydroboration of acetophenone in the chiral solvent (S)-methyl lactate exhibits moderate enantioselectivities. A six-membered transition state involving the ketone, the borane, and the lactate as the only chiral source is proposed. Molecular modeling explains the experimentally observed enantioselectivities. Calculated ee-values are in accordance with those experimentally observed. Improved ee-values (up to 60%) can be obtained in the presence of stoichiometric amounts of Lewis acid at lower reaction temperatures.

ABSTRACT:

A highly efficient transfer hydrogenation of benzoxazines, benzothiazines, and benzoxazinones with as low as 0.01 mol % binol phosphate catalyst furnishes the dihydro-2H-benzoxazines, -benzothiazines, and -benzoxazinones in good yields and with excellent enantioselectivities (see scheme). Particularly noteworthy are the mild reaction conditions and the wide scope of substrates, including sulfur-containing compounds.

ABSTRACT:

A highly efficient metal-catalyzed hydroarylation of various styrenes has been developed. This new bismuth-catalyzed C−H functionalization provides straightforward access to a series of valuable 1,1-diarylalkane products.

ABSTRACT:

A Brønsted acid catalyzed cascade transfer hydrogenation provides direct access to 2-aryl- and 2-alkyl-substituted tetrahydroquinolines with excellent enantioselectivities under mild conditions and using very low amounts of catalyst (see scheme). The best results were achieved with the binol phosphate catalyst, where Ar=9-phenanthryl, used successfully in the Strecker reaction.

ABSTRACT:

A highly efficient Bi(OTf)3-catalyzed benzylation of arenes and heteroarenes has been developed. The mild reaction conditions, high yields, operational simplicity and practicability, broad scope, and remarkably low catalyst loading render this environment friendly process an attractiv approach to diarylmethane derivatives. The extension to an intramolecular variant of this procedure provides a valuable route to substituted fluorenes.

ABSTRACT:

An optimized new chiral binol phosphate catalyst (see scheme; Ar=9-phenanthryl) for the hydrocyanation of imines provides a convenient strategy for the enantioselective synthesis of α-amino acids and diamines.

ABSTRACT:

The first metal-free Brønsted acid catalyzed hydrogenation of quinolines using Hantzsch dihydropyridine as the hydrogen source has been developed. This, so far unprecedented organocatalytic reduction of heteroaromatic compounds provides a variety of differently substituted 1,2,3,4-tetrahydroquinolines in excellent yields under mild reaction conditions using a remarkably low amount of Brønsted acid catalyst.