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Chiral Mn III –salalen and –salan Complexes Derived from ( S )‐Pyrrolidin‐2‐ylmethanamine and Their Catalytic Activity in the Asymmetric Strecker Reaction
Author(s) -
Kumar Pramod,
Saravanan S.,
Khan Noorul Hasan,
Hussain Firasat,
Singh Surendra
Publication year - 2014
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201402548
Subject(s) - chemistry , strecker amino acid synthesis , catalysis , salicylaldehyde , acetonitrile , medicinal chemistry , yield (engineering) , crystal structure , enantioselective synthesis , stereochemistry , crystallography , organic chemistry , schiff base , materials science , metallurgy
The salalen and salan ligands have been synthesized by the reactions of ( S )‐pyrrolidin‐2‐ylmethanamine and salicylaldehyde derivatives. These ligands were treated with Mn(CH 3 COO) 2 · 4H 2 O followed by air oxidation to give ( S , R )‐Mn III –salalen and –salan complexes in yields of 84–88 %. The absolute configuration of ( S , R )‐Mn III –salalen was determined by single‐crystal X‐ray diffraction and CD analysis of the ligands and complexes showed similiar Cotton effects. The Mn III –salalen and –salan complexes were screened for their catalytic activity in the asymmetric Strecker reaction. ( S , R )‐2,4‐Di‐ tert ‐butyl‐6‐({[1‐(3,5‐di‐ tert ‐butyl‐2‐hydroxybenzyl)pyrrolidin‐2‐yl]methylimino}methyl)phenolatomanganese(III) chloride (5 mol‐%) was found to be a suitable catalyst for the asymmetric Strecker reaction of N ‐(4‐methoxybenzylidene)diphenylmethanamine with ethyl cyanoformate, which gave 89 % yield and 55 % ee of 2‐(benzhydrylamino)‐2‐(4‐methoxyphenyl)acetonitrile at –15 °C after 24 h.