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- Title
Catalysis of Enantioselective Strecker Reaction in the Synthesis of D-Homophenylalanine Using Recyclable, Chiral, Macrocyclic Mn<sup>III</sup>-Salen Complexes.
- Authors
Saravanan, S.; Khan, Noor ‐ ul H.; Bera, Prasanta K.; Kureshy, Rukhsana I.; Abdi, Sayed H. R.; Kumari, Prathibha; Bajaj, Hari C.
- Abstract
A convenient approach to the asymmetric Strecker reaction was established by synthesizing chiral, mono- and dinuclear, macrocyclic MnIII-salen complexes possessing achiral and chiral linkers (trigol, piperazine, and diethyl tartarate). This group of macrocyclic complexes has emerged as improved metal-based catalysts for the enantioselective Strecker reaction of aldimines, giving high enantioselectivity (up to 99 %) for a wide range of substrates. The macrocylic complex 6 a with trigol linker works very well with TMSCN (trimethylsilyl cyanide) as a source of cyanide, using 4-phenyl pyridine N-oxide (4-PPyNO) as a co-catalyst in toluene at −40 °C. However, the macrocyclic complex 6 b with diethyl tartarate as a linker affected excellent chiral induction for both aromatic and aliphatic imines with a safer cyanide source (ethyl cyanoformate) in toluene at −20 °C in the presence of N, N-diisopropylimine as a co-catalyst. Complexes 6 a and 6 b used in the present study were recoverable and recyclable (five times) with retention of their performance at gram level. The kinetic study with complex 6 a for the enantioselective Strecker reaction of N-benzyl benzylimine revealed a first-order dependence on catalyst, substrate, and TMSCN concentration. This protocol with catalyst 6 b was further extended for the synthesis of D-homophenyl alanine, an important analogue in factor Xa inhibitors.
- Subjects
CATALYSIS; ENANTIOSELECTIVE catalysis; CHEMICAL synthesis; MACROCYCLIC compounds; ALDIMINES; CATALYSTS
- Publication
ChemCatChem, 2013, Vol 5, Issue 6, p1374
- ISSN
1867-3880
- Publication type
Article
- DOI
10.1002/cctc.201200700