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Chiral Calcium–BINOL Phosphate Catalyzed Diastereo‐ and Enantioselective Synthesis of syn ‐1,2‐Disubstituted 1,2‐Diamines: Scope and Mechanistic Studies
Author(s) -
Lalli Claudia,
Dumoulin Audrey,
Lebée Clément,
Drouet Fleur,
Guérineau Vincent,
Touboul David,
Gandon Vincent,
Zhu Jieping,
Masson Géraldine
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201405286
Subject(s) - electrophilic amination , enantioselective synthesis , chemistry , catalysis , substituent , amination , reactivity (psychology) , electrophile , combinatorial chemistry , oligomer , kinetic resolution , calcium , stereochemistry , organic chemistry , medicine , alternative medicine , pathology
A highly enantioselective, chiral, Lewis acid calcium–bis(phosphate) complex, Ca[ 3 a ] n , which catalyzes the electrophilic amination of enamides with azodicarboxylate derivatives 2 to provide versatile chiral 1,2‐hydrazinoimines 4 is disclosed. The reaction gives an easy entry to optically active syn ‐1,2‐disubstituted 1,2‐diamines 6 in high yields with excellent enantioselectivities, after a one‐pot reduction of the intermediate 1,2‐hydrazinoimines 4 . The geometry and nature of the N‐substituent of the enamide affect dramatically both the reactivity and the enantioselectivity. Although the calcium–bis(phosphate) complex was a uniquely effective catalyst, the exact nature of the active catalytic species remains unclear. NMR spectroscopy and MS analysis of the various calcium complexes Ca[ 3 ] n reveals that the catalysts exist in various oligomer forms. The present mechanistic study, which includes nonlinear effects and kinetic measurements, constitutes a first step in understanding these calcium–bis(phosphate) complex catalysts. DFT calculations were carried out to explore the mechanism and the origin of the enantioselectivity with the Ca[ 3 ] n catalysts.