Sayuri Hayashi

Synthesis of Aziridines by Palladium‐Catalyzed Reactions of Allylamines with Aryl and Alkenyl Halides: Evidence of a syn‐Carboamination Pathway

Palladium-catalyzed intramolecular carboetherification or carboamination reactions of alkenes with organic halides emerged as an attractive method to construct heterocycles, forming both carbon–heteroatom and carbon–carbon bonds in a single operation. A number of five-membered heterocycles have been synthesized by this methodology, 3] however, the preparation of strained three-membered heterocycles has remained a challenge. We have previously reported palladium-catalyzed carboetherification reactions of tertiary allyl alcohols with aryl or alkenyl halides, which provide multisubstituted epoxides. We expected that the reaction could be extended to carboamination for the synthesis of aziridines starting from allylamines. Herein we present our preliminary results of the carboamination along with evidence for a plausible reaction mechanism. Our investigation began with a reaction of N-phenylallylamine 1a bearing two phenyl groups at the allylic position (Table 1). Treatment of 1a with bromobenzene in the presence of sodium tert-butoxide under palladium catalysis led to aziridination and C C bond formation, providing the corresponding arylated aziridine 2a in 98% yield (Table 1, entry 1). In contrast to our previous epoxidation reactions, the aziridination reaction did not suffer from a competitive Mizoroki–Heck reaction. A wide range of aryl bromides and chlorides were incorporated into the corresponding aziridines 2a–2h in excellent yields (Table 1, entries 2–9). Alkenyl chlorides also proved to be suitable substrates for the aziridination reactions (Table 1, entries 10 and 11). The reactions of several N-arylallylamines with bromobenzene were then examined (Table 2). The electronic nature of aryl substituents on the nitrogen atom did not affect the efficiency of the reaction (Table 2, entries 1 and 2). Gratifyingly, alkyl-substituted allylamines 1d and 1 e also underwent the reaction in satisfactory yields (Table 2, entries 3 and 4).

Design and synthesis of new chiral phosphorus–olefin bidentate ligands and their use in the rhodium-catalyzed asymmetric addition of organoboroxines to N-sulfonyl imines

Novel chiral phosphorus-olefin bidentate ligands have been synthesized in a few steps from a readily available enantiopure compound. These ligands have been applied to a rhodium-catalyzed asymmetric addition of organoboroxines to N-sulfonyl aldimines, achieving high yield and enantioselectivity.

Synthesis of Epoxides by Palladium-Catalyzed Reactions of Tertiary Allyl Alcohols with Aryl or Alkenyl Halides

A novel synthetic method for the preparation of tri- or tetrasubstituted epoxides is reported. Treatment of readily available tertiary allyl alcohol with aryl or alkenyl halide under palladium catalysis resulted in arylative cyclization to form the epoxide. The reaction includes intramolecular C-O bond and intermolecular C-C bond construction.

Synthesis of arylallenes by palladium-catalyzed retro-propargylation of homopropargyl alcohols.

Treatment of tertiary homopropargyl alcohol with aryl halide under palladium catalysis provided arylallenes regioselectively. The reaction includes retro-propargylation, which proceeds in a concerted fashion via a cyclic transition state and transfers the stereochemistry of homopropargyl alcohols through C-C bond cleavage. The present method enables the use of homopropargyl alcohols as allenylmetal equivalents.

Nickel-Catalyzed Allylation of Allyl Carbonates with Homoallyl Alcohols via Retro-Allylation Providing 1,5-Hexadienes

A highly efficient and mild method for the synthesis of 1,5-hexadienes, nickel-catalyzed reactions of Boc-protected allyl alcohols with homoallyl alcohols, has been developed. Nickel-mediated retro-allylation allows for the use of homoallyl alcohols as allylmetal equivalents in the synthesis of 1,5-hexadienes.

Palladium-catalyzed allylation of aryl halides with homoallyl alcohols bearing a trisubstituted double bond: application to chirality transfer from hydroxylated carbon to benzylic one.

A facile route to homoallyl alcohols bearing a trisubstituted double bond has been devised. The palladium-catalyzed reactions of aryl halides with the alcohols thus synthesized result in regiospecific allyl transfer from the alcohols to aryl halides via retro-allylation, providing allylarenes having two substituents at the 1 and 2 positions of the allyl moiety. Optically active homoallyl alcohols transfer their chirality at the hydroxylated carbon to the benzylic carbon of the product.