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Efficient Diastereo‐ and Enantioselective Synthesis of exo ‐Nitroprolinates by 1,3‐Dipolar Cycloadditions Catalyzed by Chiral Phosphoramidite⋅Silver(I) Complexes
Author(s) -
Castelló Luis M.,
Nájera Carmen,
Sansano José M.,
Larrañaga Olatz,
de Cózar Abel,
Cossío Fernando P.
Publication year - 2014
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201400563
Subject(s) - chemistry , enantioselective synthesis , phosphoramidite , trifluoromethanesulfonate , catalysis , cycloaddition , combinatorial chemistry , stereochemistry , medicinal chemistry , organic chemistry , dna , biochemistry , oligonucleotide
Chiral complexes formed by privileged phosphoramidites and silver triflate or silver benzoate are excellent catalysts for the general 1,3‐dipolar cycloaddition between azomethine ylides generated from α‐amino acid‐derived imino esters and nitroalkenes affording with high dr the exo‐ cycloadducts 4,5‐ trans ‐2,5‐ cis ‐4‐nitroprolinates in high ee at room temperature. In general, better results are obtained using silver rather than copper(II) complexes. In many cases the exo‐ cycloadducts can be obtained in enantiomerically pure form just after simple recrystallization. The mechanism and the justification of the experimentally observed stereodiscrimination of the process are supported by DFT calculations. These enantiomerically enriched exo ‐nitroprolinates can be used as reagents for the synthesis of nitropiperidines, by ester reduction and ring expansion, which are inhibitors of farnesyltransferase.