John E. Feaster

New chiral phospholanes; Synthesis, characterization, and use in asymmetric hydrogenation reactions

Abstract We describe the practical synthesis of enantiomerically pure trans-2,5-disubstituted-1-phenylphospholanes which are then employed in the preparation of a new series of C2-symmetric bis- and C3-symmetric tris(phospholane) ligands. A versatile three-step route to the important chiral 1,4-diol intermediates, used in the phosphine syntheses, is outlined. Rhodium complexes bearing the new phosphine ligands were prepared and shown to act as efficient catalyst precursors for the enantioselective hydrogenation of various unsaturated substrates.

Catalytic asymmetric reductive amination of ketones via highly enantioselective hydrogenation of the CN double bond

Abstract We describe a convenient, chemoselective asymmetric reductive amination procedure for the conversion of ketones to chiral hydrazines and amines. The key step in the three-step process is enantioselective DuPHOS-Rh-catalyzed hydrogenation of the CN double bond of N-acylhydrazones. Detailed optimization studies revealed the effect of solvent, temperature, and the N-acyl group on the enantioselectivity and catalytic efficiency of the reaction. The reduction products, N-acylhydrazines, were converted to hydrazines or amines through hydrolysis or treatment with samarium(II) iodide, respectively.

Asymmetric intramolecular hydrosilylation of hydroxyketones

Abstract A procedure for the catalytic asymmetric intramolecular hydrosilylation of α- and β-hydroxyketones has been developed. A cationic rhodium (I) catalyst bearing the new chiral diphosphine (R,R)-i-Pr-DuPHOS affords the product diols in up to 93% ee.

The first practical asymmetric synthesis of R and S-Warfarin

Abstract A highly efficient synthesis of both enantiomers of warfarin Ia and Ib has been developed by using a novel two step “chiral switch” strategy and a DuPHOS-Rh(I) catalyzed asymmetric hydrogenation.

Dihydronepetalactones deter feeding activity by mosquitoes, stable flies, and deer ticks.

ABSTRACT The essential oil of catmint, Nepeta cataria L., contains nepetalactones, that, on hydrogenation, yield the corresponding dihydronepetalactone (DHN) diastereomers. The DHN diastereomer (4R,4aR,7S,7aS)-4,7-dimethylhexahydrocyclopenta[c]pyran-l(3H)-one, DHN 1) was evaluated as mosquito repellent, as was the mixture of diastereomers {mostly (4S,4aR,7S,7aR)-4,7-dimethylhexahydrocyclopenta[c]pyran-1(3H)-one, DHN 2} present after hydrogenation of catmint oil itself. The repellency of these materials to Aedes aegypti L. and Anopheles albimanus Wiedemann mosquitoes was tested in vitro and found to be comparable to that obtained with the well-known insect repellent active ingredient N,N-diethyl-3-methylbenzamide (DEET). DHN 1 and DHN 2 also repelled the stable fly, Stomoxys calcitrans L., in this study. DHN 1, DHN 2, and p-menthane-3,8-diol (PMD), another natural monoterpenoid repellent, gave comparable levels of repellency against An. albimanus and S. calcitrans. Laboratory testing of DHN 1 and DHN 2 using human subjects with An. albimanus mosquitoes was carried out. Both DHN 1 and DHN 2 at 10% (wt:vol) conferred complete protection from bites for significant periods of time (3.5 and 5 h, respectively), with DHN2 conferring protection statistically equivalent to DEET. The DHN 1 and DHN 2 diastereomers were also efficaceous against black-legged tick (Ixodes scapularis Say) nymphs.

Practical Synthesis of Methyl Z-2-(N-Acetylamino) but-2-Enoate. An Intermediate to D- and L-2-Aminobutyric Acid

Abstract Treatment of inexpensive L- or DL-threonine methyl ester with acetic anhydride and either pyridine or anhydrous sodium acetate at reflux results in dehydration yielding the N,N-diacetamide of the title compound in >80% yield. Monodeacetylation of the diacetamide with 0.1 equiv of triethylamine in methanol affords the title monoacetamido derivative 1 in nearly quantitative yield.