(Salen)Mn(III)-Catalyzed Enantioselective Intramolecular Haloamination of Alkenes through Chiral Aziridinium Ion Ring-Opening Sequence

Abstract

Asymmetric catalysis with a chiral (Salen)­Mn­(III) complex is applied successfully to highly enantioselective intramolecular haloamination reactions of alkenes through a chiral aziridinium ion ring-opening sequence. Computational and experimental studies suggested that the C5–C6 bond polarization has a major effect on the regioselectivity of the chiral aziridines ring intermediate, and steric hindrance of groups at C5 or C6 plays a minor role. Various amino-alkenes can cyclize under the reaction conditions to obtain 2-brominated/chlorinated pyrrolidine and indoline derivatives with excellent yield and enantioselectivity.

Asymmetric Synthesis of α-Spiro-γ-lactones and α-Substituted γ-Lactones via Chiral Bifunctional Sulfide-Catalyzed Bromolactonizations

“…Transformations of 2a (Scheme 6). (3S)-3-Methyl-8-[(4methylphenyl)sulfonyl]-2-oxa-8-azaspiro [4.5]decan-1-one (10). To a solution of 1a (40.2 mg, 0.10 mmol) in toluene (5 mL) were added 2,2′-azobis(isobutyronitrile) (AIBN) (4.9 mg, 0.030 mmol, 30 mol %) and tributyltin hydride (87.3 mg, 0.30 mmol).…”

“…This lack of development could be attributed mainly to the difficulty in achieving efficient enantioselective halolactonizations of α-allyl carboxylic acids. Despite numerous examples of the catalytic highly enantioselective halolactonizations of γ- or δ-substituted γ,δ-alkenyl carboxylic acids, sterically less hindered α-allyl carboxylic acids have remained challenging substrates for achieving highly enantioselective halolactonizations. , Regardless of the challenge, we attempted catalytic asymmetric bromolactonizations of 1 to obtain optically active α-spiro-γ-lactones 2 .…”

Asymmetric Palladium-Catalyzed Aminochlorination of Unactivated Alkenes

“…Sequential oxidation by NCS and direct reductive elimination of Pd IV species ( R )- int-II yielded the predominant chlorination (C–Cl) product (Scheme ). The formation of an aziridinium intermediate via an intramolecular nucleophilic attack at the carbon center of ( R )- int-II by the N moiety could be ruled out, which leads to the 5- exo aminochlorination products through a chiral aziridinium ion ring opening …”

“…17 The formation of an aziridinium intermediate via an intramolecular nucleophilic attack at the carbon center of (R)-int-II by the N moiety could be ruled out, which leads to the 5-exo aminochlorination products through a chiral aziridinium ion ring opening. 18 In conclusion, we have developed a novel Pd-catalyzed enantioselective aminochlorination of alkenes by using NCS as both oxidant and chlorination reagent, which provides easy access to a wide array of structurally diverse 3-chloropiperidines in good yields with excellent enantioselectivities. The reaction features good functional group compatibility and mild reaction conditions.…”

Synthesis of C3-halo substituted bicyclo[1.1.1]pentylamines via halosulfoamidation of [1.1.1]propellane with sodium hypohalites and sulfonamides

“…Herein, we demonstrate a novel strategy for the halo-sulfonamidation of [1.1.1]propellane to construct C3-chloro/bromo-BCPAs under mild conditions where the key intermediates N -halosulfonamides 18 were generated by sulfonamides and sodium hypohalite aqueous solution in situ . 19 This novel approach did not require the presence of any metal catalysts or additives and allowed for the direct introduction of chlorine/bromine and sulfonamide groups across the BCP core, thereby enabling diversification of synthetically valuable C3-chloro/bromo-BCPAs building blocks (Scheme 1c).…”