Joel M. Hawkins

Optically active carbon: Kinetic resolution of C76 by asymmetric osmylation

The chiral fullerene C76 was kinetically resolved by asymmetric osmylation providing an example of an optically active allotrope of a pure element. C76 recovered from the treatment of racemic C76 with OsO4 and a chiral alkaloid ligand, showed a specific rotation [α]D of -4000� (> 97 percent enantiomeric excess) and a circular dichroism spectrum corresponding to the ultraviolet spectrum. Regenerated C76 formed by reducing the asymmetrically osmylated C76 with SnCl2 was enriched in the opposite enantiomer. Analysis of the local curvature of the C76 molecule indicated that OsO4 should selectively add to 2 of the 30 types of bonds in C76. This regioselectivity was supported chromatographically and interpreted in terms of the kinetic resolution.

Threo-N,N'-Bis(.alpha.-methylbenzyl)sulfamide: a readily available chiral ligand for asymmetric lithium aluminum hydride reductions

Des cetones prochirales sont reduites de facon asymetrique a −20°C en utilisant un reactif prepare par reaction de LiAlH 4 avec le compose du titre et la N-benzylmethylamine

Substituent effects on sulfonate ester based olefinations

Abstract The anions of sulfonate esters derived from acidic alcohols olefinate carbonyl compounds. The dependence of the yield and stereochemistry of olefination on the sulfonate esters alkoxy substituent are consistent with a mechanism where apicophilic alkoxy groups promote olefination via 10-S-5 intermediate 3.

Alkene isomerizations with boron trichloride-hydrogen chloride solutions

Abstract The combination of boron trichloride and hydrogen chloride in dichloromethane at 0°C catalyzes facile alkene isomerizations in certain steroid systems which are not affected by HCl in the absence of BCl 3 .

A crystallographic analysis of C60(Buckminsterfullerene)

Crystallographic analysis of C60 grown from a hexane solution revealed a structure which is neither hexagonal nor cubic closest packed [space group P63/m, a= 33.54(1), c= 10.113(8)A]; packing models which are consistent with the Patterson map are described.

A short enantioselective synthesis of N-Boc-(2R,3R)-3-methyl-3-hydroxypipecolic acid from geraniol.

The asymmetric synthesis of (2R,3R)-3-methyl-3-hydroxypipecolic acid, a key intermediate in the synthesis of dual MMP-13/aggrecanase inhibitors, is described. The title compound is prepared in seven steps with an overall yield of 41% starting from geraniol. Key steps in the synthesis include Sharpless asymmetric epoxidation, which establishes the chiral centers, and a one-pot oxidative olefin cleavage/reductive amination sequence that closes the piperidine ring.