一價銠金屬催化1,6-烯炔環化反應 : 以β-硼酯取代不飽和酯起始之串聯反應

Abstract

本篇論文探討利用具有1,6-烯炔起始物進行銠金屬催化串聯反應。從一系列的反應設計中，發現此串聯反應能藉由β-氫消去反應所產生的氫化銠，進而將α,β-不飽和酯上的雙鍵進行氫化。此串聯反應是利用具有1,6-烯炔起始物1a以及β位為硼酯取代的α,β-不飽和酯作為親核性試劑2a進行反應。銠金屬經由與親核性試劑2a進行金屬交換反應後，和起始物上反應性較好的三鍵進行選擇性1,2-加成後，進行分子內環化反應形成烷基銠中間體，經由β-氫消去反應產生氫化銠，而經由分子內轉移使氫化銠選擇性加成至α,β-不飽和酯上的雙鍵後進行質子化反應，最終產生雙鍵被分子內產生的氫化銠氫化成單鍵的產物。This thesis describes a rhodium catalyzed cascade reaction of an 1,6-enyne strating material. Through a series designed experiments, a reaction involving hydrogenation of α,β-unsaturated ester via rhodium hydride, producedd by β-hydride elimination. This is the first example of α,β-unsaturated ester hydrogenation utilizing intramolecular producedd rhodium hydride. This cascade reaction utilized a starting material with 1,6-enyne structure 1a and a β-boronic acid acid pinacol ester (Bpin) substituded α,β-unsaturated ester as nucleophile 2a, the reaction was initiated by rhodium transmetalation with nucleophile 2a, then selective 1,2-addition with the more reactive triple bond on starting material, after intramolecular cyclization and β-hydride elimination, rhodium hydride will migrate from the newly formed olefin to the olefin on the nucleophile, after which hydrogenation takes place, foming the desired product 3aa.