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Catalytic intramolecular hydroamination of aminoallenes using titanium complexes of chiral, tridentate, dianionic imine-diol ligands

Sha, Fanrui and Mitchell, Benjamin S. and Ye, Christopher Z. and Abelson, Chase S. and Reinheimer, Eric W. and LeMagueres, Pierre and Ferrara, Joseph D. and Takase, Michael K. and Johnson, Adam R. (2019) Catalytic intramolecular hydroamination of aminoallenes using titanium complexes of chiral, tridentate, dianionic imine-diol ligands. Dalton Transactions, 48 (26). pp. 9603-9616. ISSN 1477-9226. doi:10.1039/c8dt05156a.

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Alkylation of D- or L-phenylalanine or valine alkyl esters was carried out using methyl or phenyl Grignard reagents. Subsequent condensation with salicylaldehyde, 3,5-di-tert-butylsalicylaldehyde, or 5-fluorosalicylaldehyde formed tridentate, X_2L type, Schiff base ligands. Chiral shift NMR confirmed retention of stereochemistry during synthesis. X-ray crystal structures of four of the ligands show either inter- or intramolecular hydrogen bonding interactions. The ligands coordinate to the titanium reagents Ti(NMe_2)_4 or TiCl(NMe_2)_3 by protonolysis and displacement of two equivalents of HNMe_2. The crystal structure of one example of Ti(X_2L)Cl(NMe_2) was determined and the complex has a distorted square pyramidal geometry with an axial NMe_2 ligand. The bis-dimethylamide complexes are active catalysts for the ring closing hydroamination of di- and trisubstituted aminoallenes. The reaction of hepta-4,5-dienylamine at 135 °C with 5 mol% catalyst gives a mixture of 6-ethyl-2,3,4,5-tetrahydropyridine (40–72%) and both Z- and E-2-propenyl-pyrrolidine (25–52%). The ring closing reaction of 6-methyl-hepta-4,5-dienylamine at 135 °C with 5 mol% catalyst gives exclusively 2-(2-methyl-propenyl)-pyrrolidine. The pyrrolidine products are obtained with enantiomeric excesses up to 17%.

Item Type:Article
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URLURL TypeDescription
Mitchell, Benjamin S.0000-0001-6585-2237
Takase, Michael K.0000-0001-8365-3645
Johnson, Adam R.0000-0002-7407-0533
Additional Information:© 2019 The Royal Society of Chemistry. The article was received on 30 Dec 2018, accepted on 11 Feb 2019 and first published on 12 Feb 2019. Financial support for this project was received from the National Science Foundation, NSF-MRI-1725142, the John Stauffer Fund for Summer Research in Chemistry, the Harvey Mudd College, Chemistry Department, the Thomas Poon Endowed Internship Fund, and the Dean of the Faculty at Pitzer College. There are no conflicts of interest to declare.
Funding AgencyGrant Number
John Stauffer Fund for Summer Research in ChemistryUNSPECIFIED
Harvey Mudd CollegeUNSPECIFIED
Thomas Poon Endowed Internship FundUNSPECIFIED
Issue or Number:26
Record Number:CaltechAUTHORS:20190219-131408335
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92982
Deposited By: Tony Diaz
Deposited On:19 Feb 2019 21:58
Last Modified:16 Nov 2021 16:54

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