Azusa Kondoh 교수

Treatment of alkyne with alkanethiol in the presence of a catalytic amount of cesium carbonate and a radical inhibitor in DMSO provides the corresponding adduct, (Z)-1-alkenyl alkyl sulfide, in good yield with high selectivity.

Hydrophosphination of 1-alkynylphosphines with diphenylphosphine proceeds in an anti fashion under copper catalysis, providing an easy and efficient access to a variety of (Z)-1,2-diphosphino-1-alkenes and their sulfides. The reaction is highly chemoselective and can be performed even in an aqueous medium. The reaction is reliable enough to realize a gram-scale synthesis of (Z)-1,2-diphosphino-1-alkene. Radical reduction of the diphosphine disulfides with tris(trimethylsilyl)silane yields the pa

[structure: see text]. Treatment of 1-alkynylphosphine with thiol in the presence of a catalytic amount of palladium acetate results in regio- and stereoselective anti-hydrothiolation, yielding the corresponding (Z)-1-phosphino-2-thio-1-alkene.

The reaction of tethered diynes with 1-alkynylphosphine sulfides under rhodium catalysis provides the corresponding phosphine sulfides having a bulky aryl group. The following desulfidation yields bulky phosphines that will potentially serve as ligands in transition-metal-catalyzed reactions.

A novel catalytic cyclization reaction of alkynyl α-ketoanilide was developed by utilizing the [1,2]-phospha-Brook rearrangement. This reaction involves the generation of an amide enolate via the umpolung process, that is the addition of dialkyl phosphite to a keto moiety followed by the [1,2]-phospha-Brook rearrangement, and the subsequent intramolecular addition of the enolate to an alkyne to afford 3,4-dihydro-2-quinolone derivatives. Under high-temperature reaction conditions, further rearra

A chiral bis(guanidino)iminophosphorane catalyzes enantioselective addition reactions of a 1,3-dithiane derivative as a pronucleophile. The chiral uncharged organosuperbase facilitates the addition of benzyloxycarbonyl-1,3-dithiane to aromatic N-Boc-protected imines to provide optically active α-amino-1,3-dithiane derivatives, which are valuable versatile building blocks in organic synthesis.

An efficient method for the synthesis of tetrasubstituted furans was developed by utilizing the [1,2]-phospha-Brook rearrangement under Brønsted base catalysis. The two-step one-pot formal [3 + 2] cycloaddition involves the nucleophilic addition of a propargyl anion, which is catalytically generated through the [1,2]-phospha-Brook rearrangement, to an aldehyde and the subsequent intramolecular cyclization mediated by <i>N</i>-iodosuccinimide to provide 2,4,5-trisubstituted-3-iodofurans. The pres

A Brønsted base catalyzed rearrangement reaction of 2-allyloxy-2-phosphonoacetate derivatives was developed. This reaction proceeded via a [2,3]-Wittig rearrangement followed by a phospha-Brook rearrangement. This is the first example of a catalytic [2,3]-Wittig rearrangement initiated by a Brønsted base.

The synthesis of functionalized phenanthrene derivatives was achieved by intramolecular cyclization utilizing the [1,2]-phospha-Brook rearrangement under Brønsted base catalysis. Treatment of biaryl compounds having an α-ketoester moiety and an alkyne moiety at the 2 and 2' positions, respectively, with diisopropyl phosphite in the presence of a catalytic amount of phosphazene base P2-tBu provides 9,10-disubstituted phenanthrene derivatives in high yields. This reaction involves the generation o

A new method for catalytic generation of a homoenolate equivalent and its application to carbon-carbon bond formation was developed by utilizing the [1,2]-phospha-Brook rearrangement under Brønsted base catalysis. The α-oxygenated allyl anions, which can serve as homoenolate equivalents, were catalytically generated in situ by treating readily available chalcones with diethyl phosphite or the pre-formed 1,2-adducts of diethyl phosphite with chalcones in the presence of a catalytic amount of a ph

The formal [3+2] cycloaddition of epoxides and unsaturated compounds is a powerful methodology for the synthesis of densely functionalized five-membered heterocyclic compounds containing oxygen. Described is a novel enantioselective formal [3+2] cycloaddition of epoxides under Brønsted base catalysis. The bis(guanidino)iminophosphorane as a chiral organosuperbase catalyst enabled the enantioselective reaction of β,γ-epoxysulfones with imines, owing to its strong basicity and high stereocontrolli

This Focus Review summarizes transformations of 1-alkynylphosphines and their derivatives directed toward the synthesis of new phosphines. Owing to the importance of organophosphines as ligands for transition metal catalysts, development of efficient methods for the synthesis of new phosphines is quite important. 1-Alkynylphosphines and their derivatives have been emerging as useful precursors for the creation of new phosphines. Chemical modifications of the carbon-carbon triple bonds, including

An organocatalytic nucleophilic substitution reaction of gem-difluoroalkenes with ketene silyl acetals was developed. Phosphazene P4- tBu effectively catalyzed the reaction under mild conditions to provide monofluoroalkenes possessing an alkoxycarbonylmethyl group in high yields with high Z selectivities.

An enantioselective Friedel-Crafts reaction with aliphatic ketimines generated <i>in situ</i> from hemiaminal ethers catalyzed by a chiral Brønsted acid was investigated. The reaction of 2-methoxyfuran with (thio)hydantoin-derived hemiaminal methyl ether proceeded under the influence of a chiral phosphoric acid catalyst to afford the corresponding adduct possessing a quaternary stereogenic center in high yield with high enantioselectivity. Theoretical studies were also conducted to clarify the m