GROUP VIA METAL COMPLEXES IN SYNTHESIS

点击翻译按钮获取中文摘要

DESCRIPTION: The principal goal of this proposal is the development of new methods for controlled functionalization of alkenes and dienes based on organometallic chemistry involving Group VIA transition metals. The specific focus in the 01 through 04 years will be on the manipulation of p-allyl- and diene-molybdenum complexes; other Group VIA metals are not considered at this time, but it is anticipated that preliminary results on their chemistry can be generated during the grant period. The role of an acyclic pi-allyl-Mo(CO)2Cp system in stabilizing a neighboring carbanion will be studied. Previously observed irreversible rearrangements of these carbanions will allow the construction of stereochemically defined olefinic subunits that are important structural features of many biologically important molecules. The chemistry of carbanions generated from cyclic pi-allyl-molybdenum complexes, as well as external nucleophile additions to cyclohexadiene-molybdenum complexes, will be evaluated as methodology for the construction of quaternary carbon centers. Methods for regiocontrol will be examined, leading to new approaches for the synthesis of important subunits of Amaryllidaceae alkaloids. Internal carbon nucleophile additions to diene-molybdenum complexes will be studied, leading to methodology for the construction of spirocyclic and other complex ring systems. This will be the first general study of annulation reactions of electrophilic diene complexes and will break new ground in the rapidly developing area of organic synthesis using organometallic complexes. The use of chiral auxiliaries attached to dienes and allylic bromides, to effect the synthesis of optically pure pi-allyl- and diene-molybdenum complexes, will be studied in anticipation of allowing all of the aforementioned methodology to be applied in asymmetric organic synthesis.