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Catalytic intramolecular hydroamination of aminoallenes using titanium and tantalum complexes of sterically encumbered chiral sulfonamides

Sha, Fanrui and Shimizu, Emily A. and Slocumb, Hannah S. and Towell, Sydney E. and Zhen, Yi and Porter, Hanna Z. and Takase, Michael K. and Johnson, Adam R. (2020) Catalytic intramolecular hydroamination of aminoallenes using titanium and tantalum complexes of sterically encumbered chiral sulfonamides. Dalton Transactions, 49 (35). pp. 12418-12431. ISSN 1477-9226. https://resolver.caltech.edu/CaltechAUTHORS:20200831-110816175

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Abstract

Catalysis using earth abundant metals is an important goal due to the relative scarcity and expense of precious metal catalysts. It would be even more beneficial to use earth abundant catalysts for the synthesis of common pharmaceutical structural motifs such as pyrrolidine and pyridine. Thus, developing titanium catalysts for asymmetric ring closing hydroamination is a valuable goal. In this work, four sterically encumbered chiral sulfonamides derived from naturally occurring amino acids were prepared. These compounds undergo protonolysis reactions with Ti(NMe₂)₄ or Ta(NMe₂)₅ to give monomeric complexes as determined by both DOSY NMR and X-ray crystallography. The resulting complexes are active for the ring closing hydroamination hepta-4,5-dienylamine to give a mixture of tetrahydropyridine and pyrrolidine products. However, the titanium complexes convert 6-methylhepta-4,5-dienylamine exclusively to 2-(2-methylpropenyl)pyrrolidine in higher enantioselectivity than those previously reported, with enantiomeric excesses ranging from 18–24%. The corresponding tantalum complexes were more selective with enantiomeric excesses ranging from 33–39%.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1039/d0dt02557gDOIArticle
ORCID:
AuthorORCID
Sha, Fanrui0000-0001-8310-147X
Slocumb, Hannah S.0000-0002-9440-2195
Towell, Sydney E.0000-0003-2358-0039
Porter, Hanna Z.0000-0002-7526-1905
Takase, Michael K.0000-0001-8365-3645
Johnson, Adam R.0000-0002-7407-0533
Additional Information:© 2020 The Royal Society of Chemistry. Submitted 20 Jul 2020; Accepted 21 Aug 2020; First published 21 Aug 2020. Financial support for this project was received from the National Science Foundation, NSF-MRI-1725142, the John Stauffer Fund for Summer Research in Chemistry, and Harvey Mudd College. We gratefully acknowledge NSF support for quantum mechanics calculations through the award CHE-1565743 (Robert J. Cave). The authors thank the Beckman Institute for their support of the X-Ray Crystallography Facility at Caltech and the Dow Next Generation Instrumentation Grant. There are no conflicts of interest to declare.
Funders:
Funding AgencyGrant Number
NSFMRI-1725142
John Stauffer Charitable TrustUNSPECIFIED
Harvey Mudd CollegeUNSPECIFIED
NSFCHE-1565743
Caltech Beckman InstituteUNSPECIFIED
Dow Next Generation Educator FundUNSPECIFIED
Issue or Number:35
Record Number:CaltechAUTHORS:20200831-110816175
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200831-110816175
Official Citation:Catalytic intramolecular hydroamination of aminoallenes using titanium and tantalum complexes of sterically encumbered chiral sulfonamides. Dalton Trans., 2020, 49, 12418-12431; doi: 10.1039/d0dt02557g
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105168
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:08 Sep 2020 18:15
Last Modified:17 Sep 2020 23:46

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