Enantioselective ring-opening

Fig. 2. Initial rate kinetics for the enantioselective ring opening of the ECH with HjO catalyzed by the monomer and dimer chiral (salenlCoAlXa catalysts.

Lipase catalysis is often used for enantioselective production of chiral compounds. Lipase induced the enantioselective ring-opening polymerization of racemic lactones. In the lipase-catalyzed polymerization of racemic (3-BL, the enantioselec-tivity was low an enantioselective polymerization of (3-BL occurred by using thermophilic lipase to give (/ )-enriched PHB with 20-37% enantiomeric excess (ee). ... 

The enantioselectivity was significantly influenced by the steric factor of the thiols employed. When p-MeC6H4SH and PhSH were used, the optical yields decreased to 69% and 3%, respectively. Shibasaki et al. have reported that gallium-lithium-bi-naphthoxide (GLB) 51 became a good catalyst for the enantioselective ring opening reaction of epoxide for the production of 52 (Eq. 7.39) [46]. 

The enantioselective ring opening of mew-epoxides with thiols can also be facilitated by chiral (salen)Ti(IV) complex.43 As shown in Scheme 4-25, in the presence of salen compound 71 and Ti(OPr )4, ring opening of mew-epoxide proceeds at —25° to —40°C, giving a product with good chemical yield and moderate ee. 

Scheme 12.24. Titanocene catalysts used for enantioselective ring-opening of 1.

Tiible 11. Enantioselective ring opening of various tneso-epoxides with 4-methoxyphenol (105) promoted by Ga-Ii-linked-BINOL complex (116). 

T. Iida, N. Yamamoto, N. Matsunaga, H.-G. Woo, M. Shibasaki, Enantioselective Ring Opening of Epoxides with 4-Methoxyphenol Catalyzed by Gallium Hetero-bimetallic Complexes An Efficient Method for the Synthesis of Optically Active 1,2-Diol Monoethers, Angew. Chem Int. Ed. EngL 1998,32 2223-2226. 

Figure 14.20. Jacobsen s catalyst in enantioselective ring opening of epoxide...

Scheme 18. A possible application of the enantioselective ring opening of epibromohydrin with phenols in combinatorial synthesis using the catalyst 36...

Scheme 27. Enantioselective ring opening of cyclic oxides G and H by TMSN3 catalyzed by chiral Cr(III) Schiff base complexes within the cavities of zeolites Y 53, EMT 54 and into the interlamellar region of K-10 montmorillonite 55.

Table 3 Enantioselective ring opening of cyclohexeneoxide with TMSN3 catalyzed by...

Denmark, S. E. Barsanti, P. A. Wong, K.-T. Stavenger, R. A. (1998) Enantioselective ring opening of epoxides with silicon tetrachloride in the presence of a chiral lewis base., J. Org. Chem., 63 2428-2429. 

Reymond, S. Brunei, J. M. Buono, G. (2000) New development in the enantioselective ring opening of meso-epoxides by various ion silicon sources catalyzed by an o-methoxyaryldiazaphosphonamide Lewis base., Tetrahedron Asymmetry, 11 4441-4445. 

Nakajima, M. Saito, M. Uemura, M. Hashimoto, S. (2002) Enantioselective ring opening of meso-epoxides with tetrachlorosilane catalyzed by chiral bipyridine N,N -dioxide derivatives.. Tetrahedron Lett., 43 8827-8829. 

Carree, F. Gil, R. Collin, J. (2005) Enantioselective ring opening of meso-epoxides by aromatic amines catalyzed by lanthanide iodo binaphtholates., Org. Lett., 7 1023-1026. 

Schneider, C. (2006) Synthesis of 1,2-difunctionalized fine chemicals through catalytic, enantioselective ring-opening reactions of epoxides., Synthesis, 3919-3944. 

Kureshy, R. I. Singh, S. Khan, N. H. Abdi, S. H. R. Suresh, E. Jasra. R. V. (2006) Facile enantioselective ring-opening reaction of meso-epoxides with anilines using (5)-(-)-BlNOL-Ti complex as a catalyst., Ewr. J. Org. Chem., 1303-1309. 

Al-Azemi TF, Kondaveti L, Bisht KS (2002) Solventless enantioselective ring-opening polymerization of substituted-caprolactones by enzymatic catalysis. Macromolecules 35 3380-3386... 

Enantioselective Ring-Opening Polymerizations of Substituted Lactones Using Lipases... 

Table 9. Enantioselective Ring Opening of Anhydrides with Methanol Catalyzed by Cinchona Alkaloids...

The enantioselective ring opening of meso-epoxides such as cyclohexene oxide, which uses benzoic acid as the nucleophile, was also investigated (see Scheme... 

Scheme 2.1.6.6 Enantioselective ring opening of meso-epoxides with benzoic acid.

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