A new class of chiral Mo-based complexes 2a and 2b, bearing functionalized chiral binol ligands, is disclosed. Mo complex 2a promotes the asymmetric ring-closing metathesis (ARCM) of various dienes and trienes to afford six-membered carbo- and heterocycles efficiently and in high optical purity. The binol-based chiral Mo catalysts complement the previously reported biphen-based complexes, which are particularly effective in the enantioselective synthesis of five-membered rings by ARCM. Studies regarding catalytic kinetic resolutions and asymmetric desymmetrizations are described. It is possible to obtain optically pure products in high yield from catalytic reactions without the use of solvent (cf. eq 1). The structural attributes of these complexes are detailed on the basis of the data available from an X-ray structure and variable-temperature 1H NMR studies. The results of this investigation indicate the following:  (i) The anti-Mo·THF complex exists as a mixture of diastereomers, whereas the syn isomer is formed stereoselectively. (ii) The anti-Mo isomers are likely more Lewis acidic.

In this paper we explore reactions between 13 CH 2 d 13 CH 2 and the imido alkylidene complexes, Mo(NArand Mo(NAr Cl )(CHCMe 2 -Ph)[(R)-Benz 2 Bitet] (3e). (See text for a description of Biphen and Benz 2 Bitet.) Under a variety of conditions and for various combinations of imido, alkylidene, and diolate ligands, we have observed R-substituted molybdacyclobutanes Mo(NR)(*CH 2 *CH 2 CHCMe 2 Ph)[diolate] (*C ) 13 C), unsubstituted molybdacyclobutanes Mo(NR)(*CH 2 *CH 2 *CH 2 )[diolate], olefin complexes Mo(NR)(*CH 2 dCHR)[diolate] (R ) H or CMe 2 Ph), molybdacyclopentane complexes Mo(NR)-(*CH 2 *CH 2 *CH 2 *CH 2 )[diolate], and base-free methylene complexes Mo(NR)(*CH 2 )[diolate].We also have crystallographically characterized a molybdenum ethylene complex derived from a biphenolate complex, Mo(N-2,6-Cl 2 C 6 H 3 )(CH 2 dCH 2 )[rac-Biphen](Et 2 O).

octahydro-1,1′-bi-2-naphthol was derivatized with mesityl and benzhydryl groups in the 3 and 3′ positions to give R-H 2 Mes 2 Bitet and R-H 2 -Benz 2 Bitet, respectively. Addition of R-K 2 Benz 2 Bitet to Mo(NAr)(CHCMe 2 Ph)(OTf) 2 (dme) yielded Mo(NAr)(CHCMe 2 Ph)(R-Benz 2 Bitet)(THF) (7), while addition of R-K 2 Mes 2 Bitet to Mo(NAr)(CHCMe 2 Ph)(OTf) 2 (dme) in THF gave Mo(NAr)(CHCMe 2 Ph)(R-Mes 2 Bitet)(THF) (8). Four complexes that contained the 2,6-dichlorophenylimido ligand were prepared by similar procedures, namely, Mo(NAr Cl )(CHCMe 3 )(S-Biphen)(THF) (9), Mo(NAr Cl )(CHCMe 3 )(R-Trip 2 -BINO)(THF) (10), Mo(NAr Cl )(CHCMe 3 )(R-Mes 2 Bitet)(THF) (11), and Mo(NAr Cl )(CHCMe 3 )-(R-Benz 2 Bitet)(THF) (12). X-ray studies of 8, 9, and 12 revealed them to be typical distorted trigonal bipyramids with THF and one biphenolate oxygen occupying axial positions. In 9 and 12 the alkylidene orientation was found to be syn, while in 8 the alkylidene orientation was found to be anti. Catalysts 7, 8, 9, 10, 11, and 12 were all efficient in terms of both conversion and % ee for two standard desymmetrization reactions to form dihydrofurans.