Martin Hulce

Enantiocontrolled synthesis of quaternary carbon centers. 3,3-Disubstituted cyclopentanones. (+)-α-cuparenone.

Abstract Asymmetric synthetic methodology is introduced for preparation of 3,3-disubstituted cyclopentanones, including (+)-α-cuparenone, of high enantiomeric purity.

Asymmetric synthesis using enantiomerically pure 2-(p-anisylsulfinyl)-2-cycloalkenones

Abstract Conjugate additions of many organometallic reagents to 2-(p-anisylsulfinyl)-2-cycloalkenones, 2 proceed with much greater diastereoselectivity than additions to the corresponding 2-(p-tolylsulfinyl)-2-cycloalkenones, 7. Complexation of 2 with zinc dibromide followed by addition of various Grignard reagents lead, after reductive removal of the sulfoxide, to 3-substituted cycloalkanones of higher optical purity than those obtained from 7. Addition of methyltitanium triisopropoxide to 2-(p-anisylsulfnyl)-2-cyclohexenone, 2b, in the absence of zinc dibromide, proceeds with virtually complete asymmetric induction.

Enantiocontrolled synthesis of (S)-3-substituted cycloalkanones from (s)-2-(p-tolylsulfinyl)-2-cycloalkenones and diorganomagnesium reagents.

Abstract By appropriate choice of reaction conditions, the same enantiomerically pure ( S )-(+)-2-( p -tolylsulfinyl)cycloalkenone can be converted into either an ( R )-or an ( S )-3-substituted cycloalkanone in good to excellent enantiomeric purity.

Asymmetric synthesis using organometallic reagents and optically pure vinylic sulfoxides

A new, general method is developed for preparation of various 3-substituted carbonyl compounds of very high optical purity. Application of this method is made to asymmetric synthesis of either enantiomer of 3—methylalkanoic acids, of optically pure 3-methylcyclopentanone, 3—methylcyclohexanone, 3-naphthylcyclopentanone and 3-vinylcyclopentanone j. 9,11-Seco steroid and steroid intermediate are precursors of optically pure steroidal equilenin and estrone of natural absolute configuration. The basis for this asymmetric synthetic method rests on the transfer of chirality from the sulfoxide sulfur atom to the s-carbon carbon atom during organometallic s-addition to optically pure o-carbony1 c, -ethylenic sulfoxides.

Alumina-promoted Opening of Medium Ring Epoxides: cis-Cyclooctene Oxide - trans-2-Acetoxycyclooctanol

Abstract Opening of epoxides is usually achieved homogeneously by treating oxiranes with strong acids or strong bases; several reviews of this subject are available.2 We have discovered that commercially available chromatographic -alumina promotes highly efficient heterogeneous opening of a wide range of epoxides by a variety of nucleophiles (e.g., alcohols, acetic acid, amines, mercaptans, and selenols) under extraordinarily mild (25[ddot]) and neutral conditions and that this procedure is the method of choice for clean nucleophilic opening of medium ring epoxides.3

ASYMMETRIC SYNTHESIS USING ENANTIOMERICALLY PURE SULFOXIDES

Abstract High asymmetric induction has been observed during conjugate addition of various organometallic reagents to some enantiomerically pure 2-arylsulfinyl-2-cycloalkenones. These stereocontrolled carbon-carbon bond forming reactions are discussed in terms of their mechanistic and synthetic aspects, with emphasis on (1) using the same enantiomerically pure sulfoxide to produce either an ( R )- or an ( S )-3-substituted cycloalkanone, and (2) rationalization of the results in terms of either chelated or non-chelated ketosulfoxide reactants.