Catalytic enantioselective addition of isocyanoacetate to 3-methyl-4-nitro-5-styrylisoxazoles under phase transfer catalysis conditions

Abstract

The reaction between 3-methyl-4-nitro-5-styrylisoxazoles and ethyl isocyanoacetate proceeded under phase transfer catalysis to give enantioenriched monoadducts in high enantiomeric excess (up to 99% ee). The resulting adducts were subsequently cyclised to give 2,3-dihydropyrroles and substituted pyrrolidines in identical high ees and as a single diastereoisomer.

Temperature‐Dependent Cinchona Alkaloid Squaramide‐Catalyzed Asymmetric Formal [3+2] Cycloaddition of Isocyanoacetates with β‐Trifluoromethylated Enones

“…In order to better understand the reaction profile and verify whether Michael adducts 4 were intermediates for this formal [3+2] cycloaddition reactions, the cyclization of Michael adduct 4a was carried out under the standard cycloaddition conditions. Similar to the previous reports on the organocatalyzed asymmetric addition reactions of isocyanoacetates with isatin‐derived ketimines or activated olefins, in which the initial Mannich or Michael adducts can be transformed into the cyclization products in the presence of base, the desired product 6a was obtained in high yields by using cat. 3f or 3g as catalysts (Scheme ).…”

Chiral Squaramide Catalyzed Enantioselective 1,6‐Michael Addition of Pyrazolin‐5‐ones to Styrylisoxazole Derivatives

“…The vinylogous 1,6‐Michael addition of α,β‐unsaturated‐γ‐butyrolactam to styrylisoxazoles catalyzed by chiral squaramides as hydrogen‐bonding catalysts was also reported to furnish adducts with high stereoselectivity (Figure ). In addition, the organocatalytic enantioselective 1,6‐Michael additions of 3‐isothiocyanato oxindoles, dimethyl 2‐bromomalonate, and ethyl isocyanoacetate to various 3‐methyl‐4‐nitro‐5‐alkenylisoxazoles have been explored by various research groups . However, the Michael addition reaction of pyrazolin‐5‐one derivatives with 3‐methyl‐4‐nitro‐5‐alkenylisoxazoles to afford chiral products that contain the 3‐methyl‐4‐nitroisoxazole unit has been rarely explored.…”

Stereoselective Organocatalytic Synthesis of γ,γ‐Disubstituted Butenolides

“…In the modern asymmetric synthesis, organocatalytic 1,6‐Michael addition reaction has emerged as one of the most powerful strategy for the generation of carbon‐carbon and carbon‐heteroatom bond at the remote site under high stereocontrol . A diverse range of 1,6‐Michael acceptors like dienic sulfones, linear 2,4‐dienals,, p‐ quinone methides, linear dienones, cyclic dienones, and 3‐methyl‐4‐nitro‐5‐alkenyl‐isoxazoles and Michael donors like aldehydes, 3‐substituted oxindoles,,, phenyl malonates, β ‐ketoester, and thiols,, have been employed successfully in the literature to generate wide variety of optically active Michael adducts which can be further transformed into bioactive molecules. However, 1,6‐Michael addition reaction involving two vinylogous partners has been less explored owing to their low reactivity.…”