26891-02-1Relevant articles and documents
Cook et al.
, p. 623,625 (1979)
Organocatalytic diastereo- And enantioselective oxa-hetero-Diels-Alder reactions of enones with aryl trifluoromethyl ketones for the synthesis of trifluoromethyl-substituted tetrahydropyrans
Pasha, Maira,Tanaka, Fujie
supporting information, p. 9242 - 9250 (2021/11/16)
Tetrahydropyran derivatives are found in bioactives, and introduction of the trifluoromethyl group into molecules often improves biofunctions. Here we report diastereo- and enantioselective oxa-hetero-Diels-Alder reactions catalyzed by amine-based catalyst systems that afford trifluoromethyl-substituted tetrahydropyranones. Catalyst systems and conditions suitable for the reactions to provide the desired diastereomer products with high enantioselectivities were identified, and various trifluoromethyl-substituted tetrahydropyranones were synthesized with high diastereo- and enantioselectivities. Mechanistic investigation suggested that the reactions involve a [4 + 2] cycloaddition pathway, in which the enamine of the enone acts as the diene and the ketone carbonyl group of the aryl trifluoromethyl ketone acts as the dienophile. In this study, tetrahydropyran derivatives with the desired stereochemistry that are difficult to synthesize by previously reported methods were concisely obtained, and the range of tetrahydropyran derivatives that can be synthesized was expanded. This journal is
Catalytic Enantioselective Conjugate Addition of Stereodefined Di- and Trisubstituted Alkenylaluminum Compounds to Acyclic Enones
McGrath, Kevin P.,Hubbell, Aran K.,Zhou, Yuebiao,Santos, Damián Padín,Torker, Sebastian,Romiti, Filippo,Hoveyda, Amir H.
supporting information, p. 370 - 375 (2019/12/24)
Catalytic enantioselective conjugate addition (ECA) reactions with readily accessible and stereochemically defined E-, Z-, di- and trisubstituted alkenyl aluminum compounds are disclosed. Transformations are promoted by various NHC-copper catalysts (NHC=N-heterocyclic carbene), which are derived from enantiomerically pure sulfonate imidazolinium salts. The desired products were obtained in up to 89% yield and >99:1 e.r.; the alkenyl moiety was transferred with complete retention of its stereochemical identity in all instances. The scope and limitations of the approach, key mechanistic attributes, and representative functionalization are presented as well. (Figure presented.).
Mild Chemoenzymatic Oxidation of Allylic sec-Alcohols. Application to Biocatalytic Stereoselective Redox Isomerizations
Martínez-Montero, Lía,Gotor, Vicente,Gotor-Fernández, Vicente,Lavandera, Iván
, p. 2413 - 2419 (2018/03/13)
The design of catalytic oxidative methodologies in aqueous medium under mild reaction conditions and using molecular oxygen as final electron acceptor represents a suitable alternative to the traditional oxidative transformations. These methods are especially relevant if other functionalities that can be oxidized are present within the same molecule, as in the case of allylic alcohols. Herein we apply a simple chemoenzymatic system composed of the laccase from Trametes versicolor and 2,2,6,6-tetramethylpiperidinyloxy radical (TEMPO) to oxidize a series of racemic allylic sec-alcohols into the corresponding α,β-unsaturated ketones. Afterward, these compounds react with different commercially available ene-reductases to afford the corresponding saturated ketones. Remarkably, in the case of trisubstituted alkenes, the bioreduction reaction occurred with high stereoselectivity. Overall, a bienzymatic one-pot two-step sequential strategy has been described with respect to the synthesis of saturated ketones starting from racemic allylic alcohols, thus resembling the metal-catalyzed redox isomerizations of these derivatives that have been previously reported in the literature.
