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Your search keyword '"Gregory D. Williams"' showing total 5 results
Start Over Author "Gregory D. Williams" Publisher american chemical society (acs)
5 results on '"Gregory D. Williams"'

1. Enantioselective cyclopropane syntheses using the chiral carbene complexes (SFe)- and (RFe)-C5H5(CO)(PR3)Fe:CHCH3+. A mechanistic analysis of the carbene transfer reaction

Author

Maurice Brookhart, Debra A. Timmers, Gregory D. Williams, Yumin Liu, and Emma W. Goldman

Subjects
Chemistry, Cyclopropanation, Enantioselective synthesis, General Chemistry, Biochemistry, Medicinal chemistry, Catalysis, Cyclopropane, Isopropenyl acetate, chemistry.chemical_compound, Colloid and Surface Chemistry, Electrophile, Vinyl acetate, Reactivity (chemistry), Carbene
Abstract

The enantiomerically pure acyl complexes were converted to the corresponding enantiomerically pure carbene complexes (S Fe )- and (R Fe )-C 5 H 5 (CO)(PR 3 )Fe=CHCH 3 + by using standard techniques. Enantioselective ethylidene transfer from these complexes to styrene, vinyl acetate, and isopropenyl acetate gave methylcyclopropanes in high optical yields. A mechanistic analysis of the transfer reaction is presented by using the stereochemical results obtained coupled with deuterium labeling and relative reactivity studies. It is concluded that the most likely mechanism for carbene transfer involves reaction of the olefin with the minor but more reactive synclinal isomer of C 5 H 5 (CO)(PR 3 )Fe=CHCH 3 + followed by backside attack of the developing electrophilic center at Cγ on the Fe-Cα bond. A rationale is offered for the differing diastereoselectivities of ethylidene transfer from C 5 H 5 (CO)(PR 3 )Fe=CHCH 3 + versus C 5 H 5 (CO) 2 Fe=CHCH 3 + to various olefins

Published
1991

2. Reaction of (.eta.5-MeC5H4)Mn(CO)2(THF) with PhCH2N3 to yield binuclear (.eta.5-MeC5H4)2Mn2(CO)3[.mu.-CON(CH2Ph)N2], an intermediate in the formation of benzyl isocyanate

Author

Arnold L. Rheingold, Gregory D. Williams, and Gregory L. Geoffroy

Subjects
Inorganic Chemistry, chemistry.chemical_compound, chemistry, Yield (chemistry), Organic Chemistry, Polymer chemistry, X-ray crystallography, Inorganic chemistry, Molecule, Reaction intermediate, Crystal structure, Physical and Theoretical Chemistry, Isocyanate
Published
1986

3. Addition of the osmium-methylene bond in Os3(CO)11(.mu.-CH2) to bis(triphenylphosphine)platinum to give the spiked triangular cluster Os3Pt(.mu.-CH2)(CO)11(PPh3)2. NMR investigation of the fluxional properties of Os3(CO)11(.mu.-CH2)

Author

Gregory D. Williams, Chad A. Mirkin, Marie Chantal. Lieszkovszky, Arnold L. Rheingold, and Gregory L. Geoffroy

Subjects
chemistry.chemical_classification, Stereochemistry, Organic Chemistry, chemistry.chemical_element, Nuclear magnetic resonance spectroscopy, Crystal structure, Inorganic Chemistry, chemistry.chemical_compound, chemistry, Physical chemistry, Osmium, Physical and Theoretical Chemistry, Methylene, Triphenylphosphine, Platinum, Carbene, Inorganic compound
Published
1986

4. Enantioselective cyclopropane synthesis using the chiral carbene complexes (SFeSC)- and (RFeSC)-(C5H5)(CO)(Ph2R*P)Fe:CHCH3+ (R* = (S)-2-methylbutyl). Role of metal vs. ligand chirality in the optical induction

Author

D. Timmers, James H. R. Tucker, Benedikt Hammer, Gregory D. Williams, Henri Brunner, G. Ronald Husk, and Maurice Brookhart

Subjects
Cyclopentadiene, Cyclopropanation, Ligand, Chemistry, Stereochemistry, Enantioselective synthesis, General Chemistry, Biochemistry, Catalysis, Styrene, Cyclopropane, chemistry.chemical_compound, Colloid and Surface Chemistry, Chirality (chemistry), Carbene
Abstract

Preparation de 2 complexes ethylidene diastereoisomeres (S Fe S C )- et (R Fe S C )-Cp(CO)(PPh 2 R*) Fe=CHCH 3 + (R*=(S)-methyl-2 butyl) differents seulement par leur configurations sur Fe et transfert du groupe ethylidene de ces complexes a du styrene pour donner des cis- et trans-methyl-1 phenyl-2 cyclopropanes avec de grands exces d'enantiomeres

Published
1983

5. Formyl, acyl, and carbene derivatives of Fe3(.mu.3-EPh)2(CO)9 (E = nitrogen or phosphorus). Unique examples of carbene-nitrene and carbene-phosphinidene coupling

Author

Arnold L. Rheingold, Gregory L. Geoffroy, Robert R. Whittle, and Gregory D. Williams

Subjects
Stereochemistry, Nitrene, Infrared spectroscopy, General Chemistry, Nuclear magnetic resonance spectroscopy, Reaction intermediate, Crystal structure, Biochemistry, Catalysis, NMR spectra database, chemistry.chemical_compound, Colloid and Surface Chemistry, chemistry, Phosphinidene, Carbene
Abstract

Method of preparation, results of structural analysis and stability of the derivatives of the title compounds are described. Fe/sub 3/(..mu../sub 3/ - NC/sub 6/H/sub 5/)(CO)/sub 8/ ((OCH/sub 3/CH/sub 2/)C/sub 6/H/sub 5/) contains both nitrene and carbene ligands which are well separated since the carbene has replaced one of the original cluster carbonyls. The authors believe that this cluster complex is the first to be synthesized containing both of these ligands. Fe/sub 3/(..mu../sub 3/ - PC/sub 6/H/sub 5/)(..mu.. - C/sub 6/H/sub 5/P = C(OCH/sub 3/CH/sub 2/)) (CO)/sub 9/ has a structure which illustrates the coupling of phosphinidene and carbene ligands. 17 references, 2 figures.

Published
1985

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