STEREOSELECTIVE TITANIUM-MEDIATED ALDOL REACTIONS OF MENTHYL ACETATE ENOLATES, AND ALLYLATIONS WITH BENZALDEHYDE

The enolates of (+)- and (-)-menthyl acetate, formed by transmetallation from lithium with chloro(cyclopentadienyl)bis(1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranosato-O3)titaniUM [CpTi(DAGO)2Cl] (1), react with benzaldehyde from the Re-face with high stereoselectivities (95 and 92% diastereomeri...

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Published inAustralian journal of chemistry Vol. 46; no. 5; pp. 583 - 591
Main Authors CAMBIE, RC, CODDINGTON, JM, MILBANK, JBJ, PAUSLER, MG, RUSTENHOVEN, JJ, RUTLEDGE, PS, SHAW, GL, SINKOVICH, PI
Format Journal Article
LanguageEnglish
Published COLLINGWOOD C S I R O PUBLICATIONS 01.01.1993
Subjects
Chemistry
Chemistry, Multidisciplinary
Physical Sciences
Science & Technology
ALCOHOLS
ACID
CARBOHYDRATE COMPLEXES
ENANTIOSELECTIVE ALLYLATION
ALDEHYDES
ADDITIONS
DERIVATIVES
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Summary:The enolates of (+)- and (-)-menthyl acetate, formed by transmetallation from lithium with chloro(cyclopentadienyl)bis(1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranosato-O3)titaniUM [CpTi(DAGO)2Cl] (1), react with benzaldehyde from the Re-face with high stereoselectivities (95 and 92% diastereomeric excess) when 12-crown-4 is used during the transmetallation. Use of the chiral cyclopentadienyltitanium-alpha,alpha,alpha',alpha'-tetraaryl-2,2-dimethyl-1,3-dioxolan-4,5-dimethanol (TADDOL) complex (3) gives lower diastereoselectivities (58 and 40%) but the Si-face of benzaldehyde is attacked preferentially. Transmetallation of the 2-methylprop-2-enyl moiety to CpTi(DAGO)2Cl gives an allyltitanium reagent (2) which reacts with benzaldehyde from the Re-face with 88% enantiomeric excess.
ISSN:0004-9425
DOI:10.1071/CH9930583