Mitsuhiro Yoshimatsu

Alpha-sulfanyl and alpha-selanyl propadienyl cations: regioselective generations and cycloadditions with thioamides and selemides controlled by MeNO2-H2O system.

Alpha-sulfanyl and alpha-selanyl propadienyl cations were easily generated by the catalytic system, scandium triflate-nitromethane-H(2)O in the presence of Bu(4)NHSO(4), to regioselectively afford the multifunctionalized thiazoles and selenazoles in high yields.

A regioselective addition reaction of a sulfonyl radical to conjugate enynesulfones: A convenient synthesis of 1,4-bis(arylsulfonyl)-1,3-butadiene

Abstract p -Tolyl benzeneselenosulfonate regioselectively added to the conjugate enynesulfones 1–9 gave (1 E ,3 E )-1,4-bis(arylsulfonyl)-1,3-butadienes 10–17 , which were converted to the 4-hetero atom-substituted-1-phenylsulfonyl-1,3-butadienes 18, 21 and 22 .

Propargyl Hydrazides: Synthesis and Conversion Into Pyrazoles Through Hydroamination

Pyrazoles direct: propargyl alcohols undergo hydrazination when treated with p-tosyl hydrazide in the presence of catalytic amounts of either Sc(OTf)(3) or La(OTf)(3) (see scheme; Tf=trifluoromethanesulfonyl). Propargyl hydrazides are converted into either N-tosyl or N-H pyrazoles when treated with an acid or a base, respectively. The one-step acid-catalyzed hydrazination/cyclization of propargyl alcohols directly affords pyrazoles in high yields.

A simple reduction of α-bromosulfones by cat.(PhSe)2NaBH4

Reduction of α-bromosulfones 1, 5, 13–16 by cat.(PhSe)2NaBH4 occurred siteselectively in high yields. This reduction of 1,3- or 1,4-dibromobis(sulfone) 21 and 25 was applied to intramolecular coupling reactions to give the three- and four-membered carbocycles 26–28.

A reaction of γ-chalcogen-substituted prop-2-ynyl cations with mild nucleophiles

γ-Chalcogen-substituted prop-2-ynyl cations are generated by the reactions of diethyl acetals 1 and 2 with BF3–Et2O and react with various mild nucleophiles without isomerisation to allenyl cations to afford the prop-2-ynylated products 3a–e and 5a–c in good yields.

Copper-Catalyzed Complete Regio- and Stereoselective Cyclization of 1-Aryl-3-sulfanyl-4-oxahepta-1,6-diynes Triggered by Alkynylation

Copper(I)-catalyzed alkynylation-cyclization of 4-oxahepta-1,6-diynes 1 with a wide variety of terminal alkynes proceeded to give (3E,4Z)-3-(phenylsulfanylmethylene)-4-(2-propynylidene)tetrahydrofuran-2-yl]benzenes 2aa-he in high yields with complete regio- and stereoselectivity.

Regio- and stereoselective vinylic substitution reactions of α-haloenyne sulfones

Abstract The nucleophilic vinylic substitution reaction of (E)-α-haloenyne sulfones 2, 5–8 with sodium alkoxides proceeded regioselectively to give (E)-α-alkoxyenyne sulfones 9–17 in high yields with exclusive retention of their configuration.

Synthesis of Azepines via a [6 + 1] Annulation of Ynenitriles with Reformatsky Reagents

A protocol for the direct synthesis of azepines using a hafnium(III)-catalyzed [6 + 1] annulation of N-tethered ynenitriles with Reformatsky reagents is reported. A broad range of 3-amino-2,7-dihydro-1H-azepine-4-carboxylates 4aa-4he were obtained in high yields and with excellent functional group tolerance. The copper-mediated reactions of isolable Blaise intermediates (enamino esters 3), uniquely underwent 5-endo cyclization to afford the β-2,5-dihydropyrrolyl α,β-unsaturated esters 5aa-5fc, which exhibit anticancer activity.

First synthesis of stable 5-alkyl- or 4,5-dialkyl-substituted 1,2-thiazinylium salt

Abstract 5- t -Butyl-1,2-thiazinylium 6c and rigid 5,8-ethano-5,8-dihydrobenzo[ d ]-1,2-thiazinylium salts 17 without conjugated stabilization with the aromatic ring at the 4- or 5-position of the thiazine ring have been successfully obtained as crystals.

The C-O Bond Cleavage of Cyclic Ethers with Tris(phenylseleno)-borane-Lewis Acid.

Tris(phenylseleno)borane (1) has a hard boron element and a soft selenium element, and therefore it was expected that 1 cleaves the C-O bond. Tetrahydrofuran and tetrahydropyran were cleaved with 1 in the presence of zinc iodide to produce the δ- and e-phenylseleno alcohols (7 and 8). The C(5)-O bond of 2-methyltetrahydrofuran (5) was regioselectively cleaved with 1 and a catalytic amound of tin(IV) chloride to afford the δ-phenylseleno alcohol (12). The selenoborane (1) was a weak reagent for the C-O bond-cleavage and cleaved only cyclic ethers selectively