skip to main content


Search for: All records

Creators/Authors contains: "Mitchell, Benjamin S."

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Free, publicly-accessible full text available July 3, 2024
  2. Free, publicly-accessible full text available June 12, 2024
  3. 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 2 L 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 2 L)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%. 
    more » « less