作者:G. Greg Zipp、Mark A. Hilfiker、Scott G. Nelson
DOI:10.1021/ol025607u
日期:2002.5.1
[reaction: see text] Optically active 4-substituted 2-oxetanones provide conduits for preparing 2,3-dihydro-4H-pyrone heterocycles. Enantioenriched beta-lactones are prepared by asymmetric catalytic acyl halide-aldehyde cyclocondensation reactions. Hydrazone anion-mediated beta-lactone ring opening and ensuing cyclization-dehydroamination of the derived beta-ketohydrazone afford the desired dihydropyrones
[反应:见正文]光学活性的4-取代的2-氧杂环丁酮提供了制备2,3-二氢-4H-吡喃酮杂环的通道。通过不对称催化酰基卤-醛-环缩合反应制备对映体富集的β-内酯。dra阴离子介导的β-内酯开环和随后的β-酮ke的环化-脱氢胺化反应提供了所需的二氢吡喃酮(68-81%)。最佳的内酯开环反应条件使多种旋光的4-取代的-2-氧杂环丁烷成为富对映体的2,3-二氢-4H-吡喃酮的有效前体。