作者:Jordi Bach、Cécile Blachère、Steven D. Bull、Stephen G. Davies、Rebecca L. Nicholson、Paul D. Price、Hitesh J. Sanganee、Andrew D. Smith
DOI:10.1039/b301119d
日期:——
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
对5,5-二甲基恶唑烷丁-2-酮,4,4-二甲基恶唑烷丁-2-酮和恶唑烷丁-2-酮的N-氢肉桂酰基衍生物进行DIBAL-H氢化还原后的性质研究表明,5,5 -二甲基基团对于抑制内环亲核攻击是必不可少的。例如,用DIBAL-H处理N-氢肉桂酰基-5,5-二甲基恶唑烷丁-2-酮可选择性地形成稳定的N-1'-羟烷基衍生物,该衍生物可被视为掩蔽的氢肉桂醛当量,如在碱性条件下,母体醛的产率高。在相同条件下用DIBAL-H处理N-氢肉桂酰基-4,4-二甲基恶唑烷-2-酮可提供复杂的产物混合物,包括内环裂解的甲酸酯产物。作为替代策略,用DIBAL-H还原直链和支链N-酰基-5,5-二甲基恶唑烷-2-酮衍生物,然后进行Horner-Wadsworth-Emmons反应,得到高产率的α,β-不饱和酯。N-酰基-恶唑烷酮中的α-到环外羰基分支可抑制DIBAL-H还原,但这可以通过与ZnCl2预络合来克服,随后