title: N-acyl-5,5-dimethyloxazolidin-2-ones as latent aldehyde equivalents.
abstract: A study of the properties of N-hydrocinnamoyl- derivatives of 5,5-dimethyloxazolidin-2-one, 4,4-dimethyloxazolidin-2-one and oxazolidin-2-one upon hydride reduction with DIBAL-H demonstrates that the 5,5-dimethyl-group is essential for inhibition of endocyclic nucleophilic attack. For instance, treatment of N-hydrocinnamoyl-5,5-dimethyloxazolidin-2-one with DIBAL-H results in the selective formation of the stable N-1'-hydroxyalkyl derivative which may be regarded as a masked hydrocinnamaldehyde equivalent, as treatment under basic conditions affords the parent aldehyde in excellent yield. Treatment of N-hydrocinnamoyl-4,4-dimethyloxazolidin-2-one with DIBAL-H under identical conditions affords a complex mixture of products, including the formate ester product of endocyclic cleavage. As an alternate strategy, DIBAL-H reduction of straight chain and branched N-acyl-5,5-dimethyloxazolidin-2-one derivatives, followed by a Horner-Wadsworth-Emmons reaction affords alpha,beta-unsaturated esters in good yields. Branching alpha- to the exocyclic carbonyl in N-acyl-oxazolidinones inhibits DIBAL-H reduction, but this can be overcome by precomplexation with ZnCl2, with subsequent fragmentation generating either the corresponding aldehyde or alpha,beta-unsaturated esters. The addition of ZnCl2 has been shown to increase the diastereoselectivity observed in Wadsworth-Horner-Emmons reactions of lithiated phosphonates.
authors.affiliation: The Dyson Perrins Laboratory, University of Oxford, South Parks Road, Oxford, UK OX1 3QY.
authors.forename: Jordi
authors.initials: J
authors.lastname: Bach
authors.forename: Cécile
authors.initials: C
authors.lastname: Blachère
authors.forename: Steven D
authors.initials: SD
authors.lastname: Bull
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Davies
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Nicholson
authors.forename: Paul D
authors.initials: PD
authors.lastname: Price
authors.forename: Hitesh J
authors.initials: HJ
authors.lastname: Sanganee
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Smith