Catalytic Process for Epoxide Ring-Opening with Terminal Alkynes for Carbon-Carbon Bond Formation Restricted; Files Only

Abstract

Carbon-carbon bond-forming reactions are challenging and demand the development of catalytic transformations. One of the primary gaps in knowledge is the lack of a known catalytic method for the ring-opening reaction of epoxides with terminal alkynes using mild and practical reaction conditions. The overall objective of this research project is to invent a catalytic method for the ring-opening reaction of epoxides with terminal alkynes to replace the known stoichiometric methods. We have successfully synthesized two novel pentadentate ligands that may promote a dual activation mechanism for epoxide ring-opening with terminal alkynes. Preliminary results show that both ligands in combination with diethylzinc promoted the ring-opening reaction of 1,2-epoxyhexane with phenylacetylene to give the homopropargylic alcohol; however, only the pseudoephedrine-derived ligand (L2) promoted full conversion to the homopropargylic alcohol. This supported that the pseudoephedrine-derived ligand (L2) was superior to the achiral analog of ProPhenol (L1) and thus, the substrate scope was extended with L2. The ligand-catalyzed reaction of styrene oxide and 1-decyne gave a 48 % yield of a major regioisomer from the addition to the more substituted carbon of styrene oxide and a 3.3 % yield of homopropargylic alcohol as the minor regioisomer. The pseudoephedrine derived ligand (L2) also promoted the epoxide ring-opening reaction of benzyl glycidyl ether with phenylacetylene and resulted in a 67 % yield of the corresponding homopropargylic alcohol. Finally, we have reported the first Zn-promoted epoxide ring-opening with terminal alkynes; it is a simplification from the stoichiometric method that used both n-butyllithium and BF3-OEt2.

Table of Contents

Introduction....................................................................................................                 1

Results and Discussion

                                       I.        Preparation of Novel and Achiral L1....................................                 7

                                       II.        Preparation/Purification of Novel and Chiral L2..................                 9

                                      III.        Purification of Novel and Achiral L1....................................                11

                                    IV.        Ligand Catalyzed Reactions and Control Reactions.............                 12

                                       V.        Experimentation to Improve the Zn-Catalyzed System........                20

Conclusion.....................................................................................................                 25

Experimental.................................................................................................         26

References.....................................................................................................                  43

About this Master's Thesis

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School	Laney Graduate School
Department	Chemistry
Degree	M.S.
Submission	Master's Thesis
Language	English
Research Field	Chemistry, Organic
Keyword	epoxide ring-opening with terminal alkynes dual activation catalytic transformation iterative epoxide ring-opening reaction
Committee Chair / Thesis Advisor	Frank E. McDonald, Emory University
Committee Members	Simon B. Blakey, Emory University Katherine M. Davis, Emory University

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