Novel Intramolecular Cyclocarbonylations Involving π-Alkene-Hydridoiron Intermediates: From [η5-C5H5(CO)2Fe]-Substituted (Z)-Enals toα,β-Butenolides andγ-Butyrolactones
作者:Karola Rück-Braun、Christian Möller
DOI:10.1002/(sici)1521-3765(19990301)5:3<1038::aid-chem1038>3.0.co;2-6
日期:1999.3.1
In order to broaden the application of [eta(5)-C5H5(CO)(2)Fe]-substituted enals, reaction cascades were developed for the construction of five-membered lactone skeletons, initiated by the regioselective reduction of the aldehyde functionality with sodium borohydride or K-Selectride. Depending on the iron compound and the reagent employed, alpha,beta-butenolides or gamma-lactones were obtained. The key steps in the reaction cascade for the formation of alpha,beta-butenolides involve carbonylation and reductive elimination. Labeling experiments, which were carried out to provide mechanistic details of the subsequent gamma-lactone formation, are in agreement with a reduction step which involves a pi-alkene hydridoiron intermediate. Proposed reaction pathways are given.