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Org Biomol Chem

Title:		"SuperQuat N-acyl-5,5-dimethyloxazolidin-2-ones for the asymmetric synthesis of alpha-alkyl and beta-alkyl aldehydes"
Author(s):		Bull SD; Davies SG; Nicholson RL; Sanganee HJ; Smith AD;
Address:		"Dyson Perrins Laboratory, University of Oxford, South Parks Road, Oxford, UK OX1 3 QY. steve.davies@chemistry.ox.ac.uk"
Journal Title:		Org Biomol Chem
Year:		2003
Volume:		1
Issue:		16
Page Number:		2886 - 2899
DOI:		10.1039/b305623f
ISSN/ISBN:		1477-0520 (Print) 1477-0520 (Linking)
Abstract:		"The proclivity of alpha-branched N-2'-benzyl-3'-phenylpropionyl derivatives of (S)-4-benzyl-5,5-dimethyl-, (S)-4-phenyl-5,5-dimethyl-, (S)-4-isopropyl-5,5-dimethyl-, (S)-4-benzyl- and (S)-4-benzyl-5,5-diphenyl-oxazolidin-2-ones to generate directly 2-benzyl-3-phenylpropionaldehyde upon hydride reduction with DIBAL is investigated. The (S)-4-benzyl-5,5-dimethyl-derivative proved optimal for inhibition of endocyclic nucleophilic attack, giving 2-benzyl-3-phenylpropionaldehyde in good yield upon reduction. Application of this methodology for the asymmetric synthesis of chiral aldehydes via diastereoselective enolate alkylation of a range of (S)-N-acyl-4-benzyl-5,5-dimethyloxazolidin-2-ones to afford and array of alpha-substituted-N-acyl-5,5-dimethyloxazolidin- 2-ones (85-94% de) and subsequent reduction with DIBAL afforded directly non-racemic alpha-substituted aldehydes without loss of stereochemical integrity (87-94% ee). The extension of this protocol for the asymmetric synthesis of beta-substituted aldehydes is demonstrated, via the diastereoselective conjugate addition of a range of organocuprates to (S)-N-acyl-4-phenyl-5,5-dimethyloxazolidin-2-ones which proceeds with high diastereoselectivity (generally > 95% de). Reduction of the conjugate addition products with DIBAL gives non-racemic beta-substituted aldehydes in high yields and in high ee (generally > 95% ee). This methodology is exemplified by the asymmetric synthesis of (R)-3-isopropenylhept-6-enal, which has previously been used in the synthesis of (3Z,6R)-3-methyl-6-isopropenyl-3,9-decadien-1-yl acetate, a component of the sex pheromones of the California red scale"
Keywords:
Notes:		"PubMed-not-MEDLINEBull, Steven D Davies, Stephen G Nicholson, Rebecca L Sanganee, Hitesh J Smith, Andrew D eng England 2003/09/13 Org Biomol Chem. 2003 Aug 21; 1(16):2886-99. doi: 10.1039/b305623f"