Catalytic Enantioselective α-Allylation of Deconjugated Butenolides with Aza-π-allylpalladium 1,4-Dipoles: Access to Optically Pure 2-Piperidones Bearing an All-Carbon Quaternary Stereocenter

Abstract

A palladium-catalyzed enantioselective α-allylation of deconjugated butenolides with aza-π-allylpalladium 1,4-diploes, in situ generated from palladium-mediated decarboxylation of cyclic carbamates and amide-substituted acyclic carbonates, has been successfully developed. An array of enantioenriched 2-piperidones bearing an allcarbon quaternary stereocenter were obtained in high yields with excellent enantioselectivities (up to 99% yield and 99% ee). The utility of this method was also showcased by a large-scale reaction and synthetic transformations of the product.

Progress in catalytic asymmetric α-functionalization of vinylogous nucleophilic species

“…More recently, an effective catalytic enantioselective α-allylation of β,γ-unsaturated butenolides was also disclosed by Yuan's group (Scheme 77). 93 In the developed effective strategy, cyclic carbamates 341 and amide-substituted acyclic carbonates 342 were selected as 1,4-dipole precursors for the in situ generation of π-allylpalladium 1,4-dipoles. Pd(0)/ L21 complex was the best catalyst to promote sequential α-allylation and intramolecular aminolysis of β,γ-unsaturated butenolides.…”

Fungicide-inspired precursors of π-allylpalladium intermediates for palladium-catalyzed decarboxylative cycloadditions

“…A variety of precursors with diverse structures have been invented to realize numerous useful cycloaddition reactions. On the basis of their structures, these precursors can be categorized as vinyl cyclic carbonates, 2 methylidene cyclic carbonates, 3 vinyl cyclic carbamates, 4 methylidene cyclic carbamates, 5 vinyl lactones, 6 methylidene lactones 7 and acyclic carbonates. 8 Among them, cyclic carbamates 4−5 and lactones 6,7 were usually used for synthesis of functionalized nitrogen heterocycles and carbocycles.…”

4-Vinylbenzodioxinones as a new type of precursor for palladium-catalyzed (4+3) cycloaddition of azomethine imines

“…The precursors for the formation of π-allylpalladium zwitterionic intermediates play a critical role in the cycloaddition reactions, affecting the reactivity, cycloaddition types and structure of the cycloadducts. A variety of precursors with diverse structures have been reported, such as vinyl lactones, 7 methylidene lactones, 8 vinyl cyclic carbamates, 9 methylidene cyclic carbamates, 10 vinyl cyclic carbonates, 11 methylidene cyclic carbonates, 12 vinyl lactams 13 and acyclic carbonates. 14 Among them, cyclic carbamates 9,10 and cyclic carbonates 11,12 are usually used for the synthesis of functionalized azaheterocycles and oxa-heterocycles (Scheme 1a).…”

“…A variety of precursors with diverse structures have been reported, such as vinyl lactones, 7 methylidene lactones, 8 vinyl cyclic carbamates, 9 methylidene cyclic carbamates, 10 vinyl cyclic carbonates, 11 methylidene cyclic carbonates, 12 vinyl lactams 13 and acyclic carbonates. 14 Among them, cyclic carbamates 9,10 and cyclic carbonates 11,12 are usually used for the synthesis of functionalized azaheterocycles and oxa-heterocycles (Scheme 1a). Although several types of cyclic carbonates such as allenyl cyclic carbonates, vinyl cyclic carbonates and methylidene cyclic carbonates have been reported, to the best of our knowledge, the benzo-fused cyclic carbonates have never been developed for the generation of an oxygen-containing π-allylpalladium precursor.…”