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Polymer‐Supported Highly Enantioselective Catalyst for Nitro‐Michael Addition: Tuning through Variation of the Number of H‐Bond Donors and Spacer Length
Author(s) -
TuchmanShukron Lital,
Portnoy Moshe
Publication year - 2009
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.200800749
Subject(s) - chemistry , enantioselective synthesis , moiety , michael reaction , hydrogen bond , catalysis , bifunctional , combinatorial chemistry , diamine , polymer chemistry , nitro , organic chemistry , molecule , alkyl
Two series of polymer‐bound bifunctional organocatalysts, based on chiral diamine scaffolds, were prepared by solid‐phase synthesis. The series, incorporating a single hydrogen bond donor carbamate functionality, was notably more enantioselective in the Michael reaction of acetone and nitrostyrene than the series that includes a double hydrogen bond donor urea moiety, or the polymer‐bound diamine that lacks sufficiently acidic protons. The best aminocarbamate catalyst promoted the addition of acetone to nitroolefins with enantioselectivity unmatched by known heterogeneous catalysts. Introduction of a short linear spacer between the support and the scaffold improves the activity but reduces the selectivity of the catalyst. Alternatively, an increase in the reaction yield could be induced by the benzoic acid additive.