Radical Nitrososulfonation of Propargyl Alcohols: Thiazolidine-2,4-dione-Assisted Synthesis of 5-Alykyl-4-sulfonylisoxazoles.

In this study, we discover a good NO/HNO precursor, -hydroxypyridinesulfonamide, and the regioselective radical nitrososulfonylation reaction of propargyl alcohols. Direct and unique isoxazole synthesis afforded a good-to-high yield of 5-alkyl-3-aryl-4-pyridinesulfonylisoxazoles. Copper-catalyzed aerobic oxidation could efficiently proceed in the presence of thiazolidine-2,4-dione.

Cationic indium catalysis as a powerful tool for generating α-alkyl propargyl cations for S1 reactions.

Dehydration is an abundant and promising process in chemical, biochemical, and industrial fields. Dehydration methods can contribute to building a modern and sustainable society with minimal environmental impact. Breakthrough advances in the dehydrative S1 reaction can be achieved through the discovery of new cationic indium catalysts.

Unprecedented nucleophile-promoted 1,7-S or Se shift reactions under Pummerer reaction conditions of 4-alkenyl-3-sulfinylmethylpyrroles.

A unique 1,7-S- and Se-shift reaction under Pummerer reaction conditions of 4-alkenyl-3-sulfinyl- and seleninylpyrroles was described. The usual Pummerer reaction of 4-(alkenylaminomethyl)-3-phenylsulfinylpyrroles and a successive reaction with tetrabutylammonium hydroxide (TBAH) yielded either pyrrolo[3,2-]azepines or -pyrrol-3-ylmethyl--(4-hydroxy-3-sulfanylpropyl)--toluenesulfonamides (diols). -Pummerer reactions of 3-selanylmethylpyrroles also proceeded via in situ generation of selenoxides, followed by a treatment with TBAH.

Copper-Mediated Reactions of Nitriles with Nitromethanes: Aza-Henry Reactions and Nitrile Hydrations.

In this study, the first aza-Henry reaction of nitriles with nitromethane in a CuI/CsCO/DBU system is described. The process was conveniently and directly used for the synthesis of β-aminonitroalkenes 2a-x and tolerated aryl-, alkyl-, hetaryl-, alkenyl-, and alkynylnitriles. The resulting aminonitroalkenes 2 could be successfully transformed to the corresponding 2-nitroacetophenones, 2-amino-1-halonitroalkenes, 2-alkylaminonitroalkenes, or 3-nitropyridines.

Ni-Pd Catalyzed Cyclization of Sulfanyl 1,6-Diynes: Synthesis of 1'-Homonucleoside Analogues.

The Ni-Pd catalyzed addition-cyclization of sulfanyl 1,6-diynes 2-9 with nucleobases is described. The reactions of N-tethered 1,6-diynes with N-benzoylthymine, N,N-bis(Boc)cytosine, N-benzoyluracil and N,N-bis(Boc)adenine exclusively afforded the pyrrolylmethyl and furylmethyl nucleotides in good yields. Deprotection of nucleobases was completed by treatment with acids or bases.

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.

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.

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.

Lewis acid-catalyzed propargylic etherification and sulfanylation from alcohols in MeNO₂-H₂O.

Direct scandium- and lanthanum-catalyzed etherifications of propargyl alcohols 1 and 6 in MeNO₂-H₂O provided propargyl ethers 3, 4 and 7 in high yields. In addition, reactions of 1 and 6 with thiols exclusively yielded the corresponding propargyl sulfides.

Scandium-catalyzed propargylation of 1,3-diketones with propargyl alcohols bearing sulfur or selenium functional groups: useful transformation to furans and pyrans.

Propargylations of 1,3-diketones using 3-sulfanyl and 3-selanylpropargyl alcohols 1 in MeNO(2)-H(2)O gave alkynyl ketones 2a-m, 2o-v and 6,7-dihydro-5H-cyclohexa[b]pyran-5-ones 3k-n. With some bases, the useful propargylated 1,3-diketones underwent intramolecular cyclization to give 6,7-dihydro-5H-benzofuran-4-ones 4a-i or 4,5,6,7-tetrahydrobenzofurans 5p, 6p-v.

New cyclization of 4-oxahepta-1,6-diynes bearing sulfur and selenium functional groups.

New cyclizations of 1-sulfanyl- and -selanyl-4-oxa-1,6-heptadiynes using sodium alkoxide or thiolates provided 4-alkoxymethyl-3-phenylsulfanyl- and 3,4-bis(sulfanylmethyl)furans in high yields.

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.

Scandium-catalyzed carbon-carbon bond-forming reactions of 3-sulfanyl- and 3-selanylpropargyl alcohols.

The scandium-catalyzed substitution reactions of the phenylsulfanyl and phenylselanyl propargyl alcohols 3a- i and 7a- h regioselectively proceeded to give the propargylated compounds 4 and 8 in high yields.

Scandium-catalyzed carbon-carbon bond formations using alpha-organosulfanyl and organoselanyl-alpha-fluoroacetic acid derivatives.

The scandium-catalyzed reactions of alpha-organosulfanyl and organoselanyl-alpha-fluoroacetates 1-2, acetamides 3-4 and acetonitrile 5 with soft nucleophiles proceeded to give the products 6a-b, 7a-c, 8a-c, 9a-e in good to high yields. We also successfully performed the scandium-catalyzed intramolecular cyclization reactions and obtained the unique 5-methylene-2-oxotetrahydropyrans 16-17.

Reaction of beta-ethoxyvinyl lithiums generated from phenyltellanyl- and ethyltellanylacetaldehyde diethyl acetals with aldehydes and ketones and successive hydrations.

Reactions of alpha-tellanyl-beta-ethoxyvinyl lithiums of aldehydes and ketones proceeded in good to high yields and the successive treatment with acids gave the alpha-tellanyl alpha,beta-unsaturated aldehydes. alpha-Tellanyl alpha,beta-unsaturated aldehydes easily transformed to more useful compounds.

A novel 3,4-bis(sulfenyl)- or 4-selenenyl-3-sulfenylpenta-2,4-dienylation of aldehydes using 4-ethoxy-1,2-bis(sulfenyl)- or 1-Selenenyl-2-sulfenyl-buta-1,3-dienyl lithiums.

3,4-Dichalcogenopenta-2,4-dienylation of aldehydes proceeded in good to high yields using 4-ethoxy-1-(benzenesulfenyl)-2-(methanesulfenyl)- (5), 4-ethoxy-1,2-bis(benzenesulfenyl)but-1,3-diene (6), and 1-selenenyl derivatives 7 and 8. This novel four-carbon homologation could be applied to a synthesis of 3,4,7,8-tetrakis(benzenesulfenyl)-10,10-dimethylundeca-2,4,6,8-tetraenal (20).

A novel push-pull Diels-Alder diene: reactions of 4-alkoxy- or 4-phenylsulfenyl-5-chalcogene-substituted 1-phenylpenta-2,4-dien-1-one with electron-deficient dienophiles.

5-(phenylselenenyl)- and 5-(phenylsulfenyl)-4-ethoxy-1-phenyl-2,4-pentadien-1-ones (2) and (3) underwent [4+2] cycloaddition with N-methyl and N-phenylmaleimides and successive isomerization to give the 7-benzoyl-3a,4,5,7a-tetrahydro-1H-isoindole-1,3(2H)-diones 5, 8 and 9 in good yields. The 4-ethoxy group on the 2,4-pentadien-1-one was found to be effective to facilitate the cycloaddition with dienophiles. We also performed other [4+2] cycloadditions of 2,4-pentadien-1-ones with DMAD or naphthoquinone.

Synthetic organic chemistry with 2-ethoxy-2-(phenylselenenyl)perfluoroalk-2-enenitrile: application to alpha-cyanoperfluoroacylation of aldehydes.

(Z)- and (E)-2-Ethoxyperfluoro-2-(phenylselenenyl)alk-2-enenitriles 2-4 prepared by our original method underwent transmetalation on treatment with n-BuLi or EtMgBr, and the successive reaction with aldehyde and ketones afforded the corresponding allylic alcohols 10a-f, 9a, and 11a,b in good to high yields. Hydrolysis of the alcohols gave alpha-cyano-alpha,beta-unsaturated perfluoroalkyl ketones 13a-c, 13e, 12a, and 15a. alpha-Cyanoperfluoroalkyl ketones were easily converted to alpha,beta-unsaturated 3-aryl-2-cyanoallylic alcohols 18-22 having interesting biological activities and chemical reactivities.

A new 3-(phenylseleno)allylic cation: its regioselective C-C bond formation reaction with nucleophiles.

Highly useful C-C bond formation using 2-ethoxy-3-(phenylseleno)prop-2-enal acetal 2 was examined with various Lewis acids. The reaction of 2 with the silyl enol ether in the presence of BF(3)*Et2O, ZnBr2, or SnBr4 regioselectively provided (Z)-3,4-diethoxy-5-(phenylseleno)pent-4-enophenone 5a in high yields. On the other hand, the reaction with other Lewis acids such as EtAlCl2 or SnCl4 gave 5-(phenylseleno)- 6 or non-selenopentane-1,4-dione 7, respectively.

Reactions of Diphenyl(phenylethynyl)selenonium Salts with Active Methylene Compounds and Amides: First Isolation of Oxyselenuranes [10-Se-4(C3O)] as a Reaction Intermediate.

The reaction of the diphenyl(phenylethynyl)selenonium triflate 1a with active methylene compounds 5 and t-BuOK in THF gave furan derivatives 6. The [10-Se-4(C3O)] selenuranes 8a and 8b could be isolated from the reactions with benzoylacetonitrile 5f and with 1,3-indandione 5g, respectively, as reaction intermediates. The structures of the selenuranes 8 were elucidated by X-ray crystallography and (77)Se high-resolution solid-state NMR spectroscopy.

Novel Perfluoroacyl Olefinations of Aldehydes Using β-Thio-Substituted Perfluoroalkyl Enol Ethers.

α-(Methylthio)- or α-(phenylthio)-substituted perfluoroacylolefinations of nonenolizable aldehydes using the β-lithio-β-thio-perfluoroalkyl enol ethers stereoselectively proceeded to give ()-α,β-unsaturated perfluoroalkyl ketones , , , and . The α-(thio)-α,β-unsaturated trifluoromethyl ketones were easily converted to 3-(thio)-2-(trifluoromethyl)-1,3-butadienes and , in moderate to high yields (41-85%).

Stereospecific Syntheses of 5-Alkyl-3-ethoxy-2-((phenylchalcogeno)methylene)tetrahydrofurans.

2-Ethoxy-4-(phenylchalcogeno)but-3-ynyl ketones 1-10 were reduced with LiBH(4) in Et(2)O diastereoselectively to give 5-(phenylchalcogeno)pent-4-yn-1-ols 11-20. Treatment of the phenylchalcogen-substituted alkynyl alcohols 11-20 with t-BuOK in t-BuOH provided useful (Z)-2-((phenylchalcogeno)methylene)tetrahydrofurans 21-31 stereoselectively.