A New Methodology for Ring Enlargements by the Oxy-Cope Rearrangement: Ready Access to Highly Functionalized Medium-Size Rings
作者:Paultheo von Zezschwitz、Katharina Voigt、Matthias Noltemeyer、Armin de Meijere
DOI:10.1055/s-2000-6427
日期:——
Highly functionalized cyclononenones, -decenones and -undecenones 14-19 were prepared via a sequence of twofold Heck reaction on 1,2-dibromocycloalkenes 1-3 to yield (E,Z,E)-1,3,5-hexatrienes 4-6, subsequent epoxidation of the central double bond leading to the formation of epoxides 7-9, reductive ring opening of the epoxides and oxyanion-accelerated Cope rearrangement. The stereochemical outcome of the rearrangements was highly dependent on the ring size and, particularly in the case of the cyclodecenones, on the reaction conditions. Moreover, these transformations proved to be the first examples of reversible anionic oxy-Cope rearrangements. Conversions in the presence of benzyl halides led to formation of benzylated cycloalkenones 28-31 via a domino process of rearrangement and alkylation on an intermediate enolate.
通过对 1,2-二溴环烯 1-3 进行两倍赫克反应生成 (E,Z,E)-1,3,5-己三烯 4-6、随后对中心双键进行环氧化反应生成环氧化物 7-9、环氧化物还原开环以及氧阴离子加速科普重排等一系列过程,制备了高官能度的环壬烯酮、癸烯酮和十一烯酮 14-19。重排的立体化学结果在很大程度上取决于环的大小,特别是在环癸烯酮的情况下,还取决于反应条件。此外,这些转化还被证明是可逆阴离子氧-Cope 重排的首个实例。在有苄基卤化物存在的情况下,通过中间烯醇的多米诺重排和烷基化过程,转化生成了苄基环烯酮 28-31。