The 3-thiazolidine ring represents an important structural motif in life sciences molecules. However, up to now reduction of 3-thiazolines as an attractive approach failed by means of nearly all chemical reduction technologies for imines. Thus, the development of an efficient general and enantioselective synthetic technology giving access to a range of such heterocycles remained a challenge. Here we present a method enabling the reduction of 3-thiazolines with high conversion and high to excellent enantioselectivity (at least 96% and up to 99% enantiomeric excess). This technology is based on the use of imine reductases as catalysts, has a broad substrate range, and is also applied successfully to other sulfur-containing heterocyclic imines such as 2H-1,4-benzothiazines. Moreover the effiency of this biocatalytic technology platform is demonstrated in an initial process development leading to 99% conversion and 99% enantiomeric excess at a substrate loading of 18 g/L in the presence of designer cells.

In this paper, the dehydrogenation of tetrahydroquinolines using oxovanadium(V) catalysts under mild conditions in water and oxygen atmosphere is described. This catalytic technology was successfully applied to a range of other structurally related N-heterocycles, and a reaction mechanism is proposed.

A biocatalytic reduction of 2H-1,4-benzoxazines using imine reductases is reported. This process enables a smooth and enantioselective synthesis of the resulting cyclic amines under mild conditions in aqueous media by means of a catalytic amount of the cofactor NADPH as hydride source as well as glucose as the reducing agent used in stoichiometric amounts for in situ cofactor recycling. Several substrates were studied, and the 3,4dihydro-2H-1,4-benzoxazines were obtained with up to 99% ee. In addition, the efficiency of this reduction process based on imine reductases as catalysts has been demonstrated for one 2H-1,4-benzoxazine on an elevated laboratory scale running at a substrate loading of 10 g L −1 in the presence of a tailormade whole-cell catalyst.

A method for the highly regio- and enantioselective oxidative coupling of resorcinols has been established by using dibrominated dinuclear vanadium­(V) catalyst 1c under air. When resorcinols bearing an aryl substituent were applied as substrates to the coupling, axially chiral biresorcinols were obtained as single regioisomers in high yield with up to 98% ee.