Nájera, Carmen, Sansano, Jose M., Gómez Bengoa, Enrique
Heterocycle-based bifunctional organocatalysts in asymmetric synthesis
Pure and Applied Chemistry. 2016, 88(6): 561-578. doi:10.1515/pac-2016-0403
URI: http://hdl.handle.net/10045/59654
DOI: 10.1515/pac-2016-0403
ISSN: 0033-4545 (Print)
Abstract: 
Different chiral bifunctional organocatalysts derived from trans-cyclohexane-1,2-diamine bearing different types of guanidine units able to form-hydrogen bonding activation have been designed. Conformational rigid 2-aminobenzimidazoles bearing a tertiary amino group have been used in enantioselective Michael type reactions of activated methylene compounds to nitroalkenes. The C2 symmetric bis(2-aminobenzimidazole) derivatives the appropriate organocatalyst for the conjugate addition of 1,3-dicarbonyl compounds to maleimides as well as for the SN1 reaction of benzylic alcohols with carbon nucleophiles. 2-Aminobenzimidazoles bearing a primary amino group have shown excellent catalytic activity in the Michael reaction of aldehydes to maleimides and nitroalkenes. Diastereomeric 2-aminopyrimidines bearing a prolinamide unit have been incorporated in the trans-cyclohexane-1,2-diamine scaffold and have been used for the inter- and intra-molecular direct aldol reaction under solvent-free conditions. For the Michael reaction of aldehydes with maleimides the primary amine 2-aminopyrimidine has shown excellent efficiency as organocatalyst. The bifunctional character of these organocatalysts has been demonstrated by means of DFT calculations.
Keywords:Aldols, Asymmetric synthesis, Bifunctional catalysis, Carbenium ions, 1,3-dicarbonyl compounds, Hydrogen bonding, Nitro compounds, Succinimides, TRAMECH VIII
De Gruyter
info:eu-repo/semantics/article