Investigation of the Addition of a Kinetic Bimolecular Fragment Coupling Step to the Re2O7-Catalyzed Transposition and Cyclization of Allylic Alcohols and Examination of the Effects of Acetonitrile

Anderson, Shelby (2021) Investigation of the Addition of a Kinetic Bimolecular Fragment Coupling Step to the Re2O7-Catalyzed Transposition and Cyclization of Allylic Alcohols and Examination of the Effects of Acetonitrile. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Abstract

The Re2O7-catalyzed allylic alcohol transposition, cyclization, and trapping cascade reaction developed by the Floreancig group is a synthetically versatile reaction that has been applied to the stereoselective synthesis of tetrahydropyran rings. This work expands the Re2O7-mediated allylic alcohol transposition reaction to include a kinetically controlled bimolecular fragment coupling reaction with weak π-silane nucleophiles to access the 2,6-trans tetrahydropyran ring systems. Expansion of the fragment coupling reaction to install quaternary centers and to prepare substrates bearing pre-existing stereocenters is accomplished and gives further insight into the mechanistic details of these reactions.
Solvent effects on the reaction are analyzed, with acetonitrile providing substantial rate enhancing effects to the reaction through stabilization of the oxocarbenium ion intermediate. Acetonitrile plays a crucial role in promoting the reaction in comparison to dichloromethane, enhancing the rate and facilitating the trapping of silane nucleophiles. This modification allows the fragment coupling reaction to be expanded to stereochemically complex products that have been previously inaccessible with Re2O7. Acetonitrile also provides improved stereocontrol in comparison to dichloromethane for trapping with substrates bearing a pre-existing stereocenter. Furthermore, acetonitrile promotes equilibration to thermodynamically favored products, further illustrating its advantages.

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Details

Item Type:	University of Pittsburgh ETD
Status:	Unpublished
Creators/Authors:	Creators Email Pitt Username ORCID Anderson, Shelby sma75@pitt.edu sma75
ETD Committee:	Title Member Email Address Pitt Username ORCID Committee Chair Floreancig, Paul florean@pitt.edu florean Committee Member Brummond, Kay kbrummon@pitt.edu kbrummon Committee Member Liu, Peng pengliu@pitt.edu pengliu Committee Member McDermott, Lee lam179@pitt.edu lam179
Date:	20 January 2021
Date Type:	Publication
Defense Date:	25 November 2020
Approval Date:	20 January 2021
Submission Date:	4 December 2020
Access Restriction:	No restriction; Release the ETD for access worldwide immediately.
Number of Pages:	186
Institution:	University of Pittsburgh
Schools and Programs:	Dietrich School of Arts and Sciences > Chemistry
Degree:	PhD - Doctor of Philosophy
Thesis Type:	Doctoral Dissertation
Refereed:	Yes
Uncontrolled Keywords:	synthetic methodology; rhenium oxide; allylic alcohol transposition; stereoselective synthesis; tetrahydropyran ring synthesis; heterocycles; solvent effects
Date Deposited:	20 Jan 2021 18:05
Last Modified:	20 Jan 2021 18:05
URI:	http://d-scholarship.pitt.edu/id/eprint/40006

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