- Asymmetric ring-closing metathesis reactions
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A composition and method for the catalytic conversion of a racemic mixture of dienes to a cyclic olefin by a ring-closing metathesis (RCM) reaction are disclosed. The composition, a transition metal complex with an M=C reaction site, contains a bidentate dialkoxide of at least 80% optical purity. Because the M=C reaction site is of a sufficient shape specificity, conferred in part by the dialkoxide of sufficient rigidity and an M=N-R1 site, reacting the composition with a mixture of two enantiomeric dienes results in an olefin metathesis product that has at least a 50% enantiomeric excess of one enantiomer in the mixture. A method is also provided for reacting a composition with a racemic diene mixture to generate a metathesis product that has an enantiomeric excess of at least 50%.
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- Asymmetric ring-closing metathesis reactions involving achiral and meso substrates
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A composition and method for the catalytic conversion of a racemic mixture of dienes to a cyclic olefin by a ring-closing metathesis (RCM) reaction are disclosed. The composition, a transition metal complex with an M═C reaction site, contains a bidentate dialkoxide of at least 80% optical purity. Because the M═C reaction site is of a sufficient shape specificity, conferred in part by the dialkoxide of sufficient rigidity and a M═N—R1site, reacting the composition with a mixture of two enantiomeric dienes results in an olefin metathesis product that has at least a 50% enantiomeric excess of one enantiomer in the mixture. A method is also provided for reacting a composition with a racemic diene mixture to generate a metathesis product that has an enantiomeric excess of at least 50%. Methods are also provided for catalytic enantioselective desymmetrization. One method involves an olefin metathesis reaction with a molecular substrate having a plane of symmetry to form a product free of a plane of symmetry. Another method provides a desymmetrization reaction to occur in the absence of solvent. A method for producing quaternary carbon centers through a desymmetrization reaction is also described.
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Page column 26
(2010/01/30)
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- Synthesis of molybdenum imido alkylidene complexes that contain 3,3′-dialkyl-5,5′,6,6′-tetramethyl-1,1′-biphenyl-2, 2′-diolates (alkyl = t-Bu, adamantyl). Catalysts for enantioselective olefin metathesis reactions
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Two 3,3′-dialkyl-5,5′,6,6′-tetramethyl-1,1′-biphenyl- 2,2′-diols (where alkyl = t-Bu, adamantyl) were prepared in two steps and resolved as the menthol phosphate derivative. Addition of the dipotassium salt of each biphenolate to various Mo(N-Aryl)(CHR) (
- Alexander,Schrock,Davis,Hultzsch,Hoveyda,Houser
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p. 3700 - 3715
(2008/10/08)
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