Epoxides with thiols

Hou reported the use of a chiral (salen)titanium catalyst for the desymmetriza-tion of meso-epoxides with thiols (Scheme 7.14). The complex, fonned in situ... 

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. 

Wu, M. H. Jacobsen, E. N. (1998) Asymmetric ring opening of meso-epoxides with thiols enantiomeric enrichment using a bifunctional nucleophile., J. Org. Chem., 63 5252-5254. 

Conceptually new multifunctional asymmetric two-center catalysts, such as the Ln-BINOL derivative, LnMB, AMB, and GaMB have been developed. These catalysts function both as Brpnsted bases and as Lewis acids, making possible various catalytic, asymmetric reactions in a manner analogous to enzyme catalysis. Several such catalytic asymmetric reactions are now being investigated for potential industrial applications. Recently, the catalytic enantioselective opening of meso epoxides with thiols in the presence of a heterobimetallic complex has... 

The other side of the coin is specific base catalysis (SBC) which usually involves the removal of a proton from the substrate in a fast pre-equilibrium step followed by a rate-determining reaction of the anion. Most of the base-catalysed reactions you are familiar with work by SBC. Examples include opening of epoxides with thiols. 

The ring opening of epoxides with thiols provides an efficient route for the formation of (3-hydroxy sulfides. A one-pot method for the direct synthesis of (3-hydroxy sulfoxides has been developed <07JOC4524>. Treatment of an epoxide with PhSH, Ga(O IT)3, and H202 directly provides the sulfoxide with little to no over oxidation. 

Heterogenous metal tartrates were screened for their efficacy in the catalysis of the asymmetric ring opening of me o-2,3-disubstituted epoxides with thiols, aniline, and trimethylsilyl azide [72]. Whereas the enantioselectivity of Zn(II) tartrates is in the 15-85 % ee range, selectivity with the Mn(II), Fe(II), and Co(II) tartrates was lower (< 40 % ee). With Nugent s Zr(Of-Bu)4/C3-symmetric tetradentate ligand catalyst... 

Ring opening of 1,2-epoxides with thiol-derived nucleophiles is a well established route to /3-hydroxy sulfides that has been applied for the preparation of allylic alcohols, cyclic sulfides, thioketones, and important intermediates for the synthesis of... 

Antilla developed a catalytic enantioselective desymmetrisation of meso-epoxides with thiols by using chiral lithium phosphate 17. A wide range of epoxides and aromatic thiols were observed with high enantioselectivities (Scheme 2.12). ... 

Scheme 2.12 Enantioselective desymmetrisation of meso-epoxides with thiols with the use of chiral lithium(i) phosphate.

SCHEME 5.12 Ring opening of epoxides with thiol ate anions [13]. 

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