Switching Electrophile Intermediates to Nucleophiles: Michael and Oxa-Diels–Alder Reactions to Afford Polyoxy-Functionalized Piperidine Derivatives with Tetrasubstituted Carbon
作者:Lingaiah Maram、Fujie Tanaka
DOI:10.1021/acs.orglett.0c00735
日期:2020.4.3
Michael, Michael-annulation, and oxa-Diels–Alder reactions of carbohydrate derivatives that afford polyoxy-functionalized piperidine derivatives bearing tetrasubstituted carbon at the 3-position of the piperidine ring are reported. Iminium ions generated from carbohydrate derivatives with amines were converted to enamines in situ, which acted as nucleophiles. As a result, substituents were introduced at
Diastereo- and Enantioselective Synthesis of Functionalized Dihydropyrans via an Organocatalytic Claisen Rearrangement/Oxa-Michael Addition Tandem Sequence
rearrangement/oxa-Michael addition tandem sequence with a cinchona squaramide catalyst was described, which afforded a practical and atom-economical approach to access a range of valuable dihydropyrans in good to excellent yields with excellent stereoselectivities. The organo-bifunctional catalyst played a key role in enhancing stereoselectivity in this asymmetrictandem sequence. Moreover, the asymmetric catalytic
Thiophosphoramide catalyzed asymmetric Michael addition of acetone to functionalized nitrostyrenes: a convenient approach to optically active tetrahydropyrans
Thiophosphoramide 5d was found to be an effective organocatalyst for the enantioselective Michael reaction of problematic acetone to various hydroxymethyl nitrostyrenes, affording the multisubstituted tetrahydropyrans with three stereogenic centers. The Michael addition products generated were obtained as a single diastereomer with enantioselectivities ranging from 46% to 74% ee. (C) 2010 Elsevier Ltd. All rights reserved.