Investigation of Methods for Seven-Membered Ring Synthesis: A Practical Synthesis of 4-Oxo-5,6,7,8-tetrahydro-4H-cyclohepta[<i>b</i>]furan-3-carboxylic Acid
作者:John A. Ragan、Jerry A. Murry、Michael J. Castaldi、Alyson K. Conrad、Brian P. Jones、Bryan Li、Teresa W. Makowski、Ruth McDermott、Barb J. Sitter、Timothy D. White、Gregory R. Young
DOI:10.1021/op0102159
日期:2001.9.1
the title compound. The first scale-up route is outlined in Scheme 2 and utilizes a ring-expansion strategy to prepare cycloheptane-1,3-dione from cyclopentanone, via a [2 + 2] cycloaddition between dichloroketene and the silyl enol ether of cyclopentanone. The diketone is converted to the title compound by condensation with ethyl bromopyruvate and base, followed by acid hydrolysis. This route was efficient
描述了几种合成 4-oxo-5,6,7,8-四氢-4H-环庚[b]呋喃-3-羧酸 (1) 的路线,并讨论了每种路线的放大问题。七元环的形成是这些合成的关键问题,并提出了几种策略,包括从 cycloheptane-1,3-dione 制备、扩环路线、Dieckmann 环化、乙炔-呋喃 [4 + 2] 环加成和 Friedel − 工艺循环。其中两条路线在中试工厂中按比例放大以提供千克量的标题化合物。第一个放大路线在方案 2 中概述,并利用扩环策略通过二氯乙烯酮和环戊酮的甲硅烷基烯醇醚之间的 [2 + 2] 环加成,从环戊酮制备环庚烷-1,3-二酮。通过与溴丙酮酸乙酯和碱缩合,然后酸水解,将二酮转化为标题化合物。这条路线在实验室规模上是有效的,但在扩大规模时遇到了问题,因为竞争片段......