Molybdenum-Catalyzed Asymmetric Ring-Closing Metathesis Research Articles

Molybdenum-Catalyzed Enantioselective Synthesis of Planar-Chiral (η5-Phosphacyclopentadienyl)manganese(I) Complexes and Application in Asymmetric Catalysis

Enantioselective desymmetrization of Cs-symmetric (η5-2,5-dialkenylphospholyl)(allyldiphenylphosphine)manganese(I) dicarbonyl complexes 1 was realized by molybdenum-catalyzed asymmetric ring-closing metathesis (ARCM), and the corresponding bridged planar-chiral phosphacymantrene derivatives 2 were obtained in good yields with excellent enantioselectivity. The enantioselectivity of the ARCM reaction was strongly influenced by the structures of the phospholyl-bound alkenyl groups, and the highest enantioselectivity of up to 99% ee was achieved in the reaction of 1d,e, which possess the 2-methylpropenyl substituents at the 2- and 5-positions of the η5-phospholides. Single-enantiomeric planar-chiral 2d, which was obtained by the recrystallization of the highly enantiomerically enriched ARCM product, can serve as a chiral ligand for the palladium-catalyzed asymmetric allylic alkylation to show good enantioselectivity in up to 74% ee.

Kinetic Resolution of Planar-Chiral (η5-Bromocyclopentadienyl)manganese(I) Complexes by Molybdenum-Catalyzed Asymmetric Ring-Closing Metathesis

Kinetic resolution of racemic planar-chiral (η5-1-alkenyl-2-bromocyclopentadienyl)manganese(I) complexes 1 was realized by the molybdenum-catalyzed asymmetric ring-closing metathesis. While vinyl-Cp derivative 1a was resolved in excellent enantioselectivity with the krel values of up to 127, the selectivity in the ARCM reaction of allyl-Cp derivative 1b was modest (krel = 3.0). ARCM product 2a, which was obtained in an enantiomerically pure form by the two successive ARCM reactions or recrystallization of the enantiomerically enriched products, was found to be a versatile synthetic precursor to various planar-chiral cymantrene derivatives.

Kinetic Resolution of Planar-Chiral Ferrocenylphosphine Derivatives by Molybdenum-Catalyzed Asymmetric Ring-Closing Metathesis and Their Application in Asymmetric Catalysis

Highly enantioselective kinetic resolution of racemic planar-chiral metallocenylphosphine sulfides was realized by the molybdenum-catalyzed asymmetric ring-closing metathesis reaction with the krel values of up to 147. The enantiomerically enriched 1,4-but-2-enylene-bridged ferrocenylphosphine sulfides thus obtained could be purified to enantiomerically pure forms by simple recrystallization from hot methanol, and subsequent reduction of the phosphine sulfides provided the corresponding planar-chiral phosphines with retention of the enantiomeric homogeneity. This is a rare example of preparing planar-chiral ferrocenylphosphines by catalytic asymmetric reactions. The single-enantiomer planar-chiral ferrocenylphosphines were applied as chiral ligands in the rhodium-catalyzed asymmetric 1,4-addition reaction (the Hayashi–Miyaura conjugate addition reaction) of phenylboronic acid to 2-cyclohexenone to show excellent enantioselectivity and high yields. The NMR studies clarified that the butenylene-bridged ferr...

ChemInform Abstract: Simultaneous Induction of Axial and Planar Chirality in Arene‐Chromium Complexes by Molybdenum‐Catalyzed Enantioselective Ring‐Closing Metathesis.

The molybdenum-catalyzed asymmetric ring-closing metathesis of the various Cs -symmetric (π-arene)chromium substrates provides the corresponding bridged planar-chiral (π-arene)chromium complexes in excellent yields with up to >99 % ee. With a bulky and unsymmetrical substituent, such as N-indolyl or 1-naphthyl, at the 2-positions of the η(6) -1,3-diisopropenylbenzene ligands, both biaryl-based axial chirality and π-arene-based planar chirality are simultaneously induced in the products. The axial chirality is retained even after the removal of the dicarbonylchromium fragment, and the chiral biaryl/heterobiaryl compounds are obtained with complete retention of the enantiopurity.

Enantioselective Desymmetrization of 1,2,3-Trisubstituted Metallocenes by Molybdenum-Catalyzed Asymmetric Intraannular Ring-Closing Metathesis

Enantioselective desymmetrization of Cs-symmetric (η5-1,2,3-triallylic indenyl)M(II) complexes (1; M = Fe or Ru) was realized by the molybdenum-catalyzed asymmetric ring-closing metathesis, and the corresponding planar-chiral metallocenes 2 were obtained in good yields with high enantioselectivity of up to 98% ee.

Enantioselective Synthesis of Macrocyclic Heterobiaryl Derivatives of Molecular Asymmetry by Molybdenum‐Catalyzed Asymmetric Ring‐Closing Metathesis

AbstractWinding vine‐shaped molecular asymmetry is induced by enantioselective ring‐closing metathesis with a chiral molybdenum catalyst. The reaction proceeds under mild conditions through an E‐selective ring‐closing metathesis leading to macrocyclic bisazoles with enantioselectivities of up to 96 % ee.

Enantioselective synthesis of macrocyclic heterobiaryl derivatives of molecular asymmetry by molybdenum-catalyzed asymmetric ring-closing metathesis.

Winding vine-shaped molecular asymmetry is induced by enantioselective ring-closing metathesis with a chiral molybdenum catalyst. The reaction proceeds under mild conditions through an E-selective ring-closing metathesis leading to macrocyclic bisazoles with enantioselectivities of up to 96% ee.

Simultaneous induction of axial and planar chirality in arene-chromium complexes by molybdenum-catalyzed enantioselective ring-closing metathesis.

The molybdenum-catalyzed asymmetric ring-closing metathesis of the various Cs -symmetric (π-arene)chromium substrates provides the corresponding bridged planar-chiral (π-arene)chromium complexes in excellent yields with up to >99 % ee. With a bulky and unsymmetrical substituent, such as N-indolyl or 1-naphthyl, at the 2-positions of the η(6) -1,3-diisopropenylbenzene ligands, both biaryl-based axial chirality and π-arene-based planar chirality are simultaneously induced in the products. The axial chirality is retained even after the removal of the dicarbonylchromium fragment, and the chiral biaryl/heterobiaryl compounds are obtained with complete retention of the enantiopurity.

Kinetic Resolution of Planar‐Chiral 1,2‐Disubstituted Ferrocenes by Molybdenum‐Catalyzed Asymmetric Intraannular Ring‐Closing Metathesis

Planar chirality: Ring-closing metathesis of 1,2-diallylmetallocenes afforded the corresponding 4,7-dihydroindenyl species in high yields. The metallocenes are planar chiral with two different allylic substituents, and kinetic resolution of the racemic 1,2-diallylmetallocene derivatives was realized by molybdenum-catalyzed asymmetric ring-closing metathesis with excellent enantioselectivity (see scheme).

Enantioselective Synthesis of Planar-Chiral Phosphaferrocenes by Molybdenum-Catalyzed Asymmetric Interannular Ring-Closing Metathesis

Enantioselective synthesis of planar-chiral phosphaferrocenes was realized for the first time by molybdenum-catalyzed asymmetric ring-closing metathesis (ARCM) in up to 99% ee, which is the first application of ARCM to induction of chirality in molecules devoid of stereogenic centers.

Kinetic Resolution of Planar-Chiral Ferrocenes by Molybdenum-Catalyzed Enantioselective Metathesis

Kinetic resolution of planar-chiral 1,1‘-diallylferrocene derivatives was realized by molybdenum-catalyzed asymmetric ring-closing metathesis with excellent enantioselectivity. This is the first ex...