Date of Award
Summer 1998
Document Type
Dissertation - Restricted
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
First Advisor
Yi, Chae S.
Second Advisor
Donaldson, William A.
Third Advisor
Haworth, Daniel T.
Abstract
Transition metal-mediated coupling reaction of alkynes and alkenes is of considerable current interest because it is an attractive method for the synthesis of natural products as well as building blocks for further structural elaborations. A number of transition metal based catalyst systems are currently known to catalyze the dimerization of terminal alkynes, often with low regio- and stereoselectivity. Understanding the detailed mechanism of the dirnerization and the factors governing regio- and stereoselectivity is essential for future design of catalysts. In recent years, a fewer transition metal catalyst systems have been developed which enhanced both efficiency and selectivity. Selectivity (chemo-, regio-, diastereoand enantioselectivity) of products can be achieved by varying the metal and/or ligands electronically and sterically. Recent developments in this field include the formation of 1,3-disubstituted enynes from the head-to-tail dimerization of alkynes, and of 1,4- disubstituted enynes and the cumulenes form the head-to-head dimerization. The efficiency of the homo-coupling reaction of alkynes made it a challenge that the cross-coupling processes of different alkynes as well as alkynes with alkenes could dominate. Only few examples have been reported and neither the detailed mechanistic studies nor the factors governing the regio- and stereochernistry have been well understood. Our research goal is to study the coupling reactions of alkynes and alkenes and to probe the reaction mechanisms involved with the hope of developing better catalysts.