Andrew E. Greene

Asymmetric induction in the cycloaddition reaction of dichloroketene with chiral enol ethers. A versatile approach to optically active cyclopentenone derivatives.

Abstract Significant asymmetric induction has been observed in the cycloaddition reaction of dichloroketene with chiral enol ethers. The resultant diastereomeric cyclobutanones have been converted to synthetically useful α-chlorocyclopentenones in optically active form.

A Safe, Simple, One-Pot Preparation of N-Derivatized β-Amino Alcohols and Oxazolidinones from Amino Acids

Abstract N-tert-Butoxycarbonyl, N-benzoyl, N-benzyloxycarbonyl, and oxazolidinone derivatives of β-amino alcohols have been prepared from amino acids in 72 to 90 % yields through lithium aluminum hydride reduction followed by in situ derivatization.

ASYMMETRIC INDUCTION STUDIES IN THE INTRAMOLECULAR PAUSON-KHAND CYCLIZATION OF 7-ALKOXY-1-HEPTEN-6-YNES

Abstract Asymmetric induction has been achieved in the intramolecular Pauson-Khand reaction of 7-alkoxy-1-hepten-6-ynes derived from chiral alcohols. The stereochemical outcome of the reaction can be explained by the intermediacy of a cis-cobaltabicyclooctane.

Practical asymmetric version of the intermolecular pauson-khand reaction

Abstract The first practical asymmetric version of the intermolecular Pauson-Khand reaction has been developed based on novel chiral (non-racemic) alkoxy acetylene dicobalt hexacarbonyl complexes. The major adduct from (1R, 2S)-2-phenylcyclohexyloxyethyne and norbornadiene, isolated in 58% yield, is shown to be useful for obtaining chiral 4-substituted 2-cyclopentenones.

Camphor-derived alcohols as chiral auxiliaries for asymmetric Pauson-Khand bicyclizations. Enantioselective synthesis of α-methoxyenones

Abstract The intramolecular Pauson-Khand reaction of enol and ynol ethers of Oppolzers camphor-derived neopentyloxy alcohols is described. Bicyclic products are obtained in yields of up to 65% and with diastereoselectivities as high as 94:6 under very mild reaction conditions. The absolute configurations of the major stereoisomers obtained when (1R, 2S, 3R, 4S)-3-neopentyloxy-1,7,7-trimethylbicyclo- [2.2.1]heptan-2-ol is used as a chiral auxiliary are rationalized on the basis of the theoretically predicted preferential conformations of model precursors. A simple procedure for obtaining auxiliary-free, enantiopure bicyclic α-methoxyenones is also presented.

Improved preparation of angelate esters

Abstract A new procedure has been developed for the efficient preparation of angelate esters from alcohols. The alcohol is treated in dry toluene at 70–80 °C for 19–36 h with a mixed anhydride prepared from angelic acid and 2,4,6-trichlorobenzoyl chloride. In the absence of base, no tiglate ester is produced.

Efficient, large-scale preparation of (R)- and (S)-1-(2,4,6-triisopropylphenyl)ethanol, versatile chiral auxiliary for cyclopentenone, γ-butyrolactone, and γ-butyrolactam synthesis

Abstract A particularly efficacious, low-cost preparation of both ( R )- and ( S )-triisopropylphenyl)- ethanol , useful chiral controllers in the dichloroketene—enol ether cycloaddition reaction, has been developed.

Iterative three-carbon annelations. Synthesis of (±)-hirsutene

Abstract A short, flexible approach to the tricyclopentanoid carbon skeleton of the hirsutane group is illustrated by the synthesis of (±)-hirsutene (3).

Expedient approach to chiral cyclobutanones:asymmetric synthesis of cyclobut-G

An efficient one-pot asymmetric synthesis of cyclobutanones from chiral enol ethers is described. The approach is illustrated with alkyl- and functionalized alkyl-substituted enol ethers (nine examples). A new enantioselective synthesis of cyclobut-G (Lobucavir) could thus be achieved.

Asymmetric synthesis of bicyclo[4.3.0]nonan-8-ones by intramolecular Pauson-Khand reaction

Abstract The intramolecular Pauson-Khand reaction of (E)-1-alkoxy-1-octen-7-ynes derived from (1S,2R)-2-phenylcyclohexanol is described. 7-Alkoxybicyclo[4.3.0]non-1(9)-en-8-ones are obtained in yields up to 65% and with diastereoselectivities higher than 10:1. The absolute configuration of the major diastereomer obtained has been ascertained and can be rationalized on the basis of the preferential conformation of the precursor.