Takehiko Nishio

Sulfur-containing heterocycles derived by the reaction of hydroxy-amides and Lawesson's reagent

Abstract A simple one-pot reaction between hydroxy-amides (1) located, 1,3- or 1,4- to each other, and Lawessons reagent (LR) gives sulfur-containg heterocycles such as tetrahydrothiophene-2-imines (4), tetrahydrothiophene-2-thione (5) and tetrahydrothiopyrandash2-thione (6). Similar reaction of 3-N-acylamino-alcohols (7) affords thiazoline derivatives (9).

Stereoselective Synthesis of 4H-5,6-Dihydro-1,3-thiazines by the Reaction of 3-N-Acylamino Alcohols with Lawesson’s Reagent

The 4H-5,6-Dihydro-1,3-thiazine derivatives 13−15 were obtained exclusively and stereoselectively in fair yields by treating the 3-N-acylamino alcohols 5−8 with an equimolar amount of Lawesson’s reagent (LR), while the corresponding thiols 9−12 were afforded stereoselectively when only 0.5 equiv. of LR was used in this reaction.

Thionation of ω-hydroxy amides with Lawesson's reagent: Synthesis of thioenamides and sulfur-containing heterocycles

Abstract The thionation of ω-hydroxy amides with Lawessons reagent [LR: 2,4-bis(p-methoxyphenyl)-1,3,2,4-dithiaphosphetane-2,4-disulfide] is described. The treatment of 3-hydroxy amides 1 with LR exclusively gave thioenamides 2 in fair yields. The treatment of 4-hydroxy amides 5 with LR yielded sulfur-containing heterocycles such as tetrahydrothiophene-2-imines 6 and tetrahydrothiophene-2-thione 7a through cyclization of intermediates, 4-mercapto amides 8. The 5-hydroxy amides 13 also reacted with LR to afford tetrahydrothiopyrane-2-thione 14 as the the sole product.

Nuclear magnetic resonance spectral study of β-aminoenones

The n.m.r. spectra of the four geometrical isomers of β-aminoenones, trans-s-trans, trans-s-cis, cis-s-trans, and cis-s-cis, are discussed. It was found that the chemical shift of the α-proton of β-aminoenones depends on both anisotropic effects and the electron density: δ=δ0–Δδstruc=ΔδAr+K(q–q0). Thus the conformation of non-rigid β-aminoenones can be determined from the observed and the calculated chemical shifts of the α-proton.

First Preparation of Dibenzo(bc,fg)(1,4)dithiapentalene and Determination of the Structure by X-Ray Analysis.

Abstract New stable dibenzo[ bc,fg ][1,4]dithiapentalene ( 1 ) was prepared by heating 1,9-bis(methylthio)-dibenzothiophene in a glass tube. The X-ray analysis of 1 reveals clearly that it has a completely planar structure. Repeated scanning of cyclic voltammetry of 1 shows an analogous voltammogram with that of polythiophene.

New and stable endoperoxide from the pteridin-2,4,7-trione and singlet oxygen

Abstract 1,3,8-Trimethyl-6-phenylpteridin-2,4,7-trione (1) reacted with singlet oxygen to give the pteridin-2,4,7-trione 6,8′-endoperoxide (2), which on warming generates singlet oxygen. Generation of singlet oxygen from thermolysis of the endoperoxide (2) was confirmed by trapping experiments using typical singlet oxygen acceptors.

Reduction of β-arylthio- or β-alkylthio-αβ-unsaturated ketones

The preparation and reduction of β-arylthio- or β-alkylthio-αβ-unsaturated ketones (1) with lithium aluminium hydride or sodium borohydride have been examined. Reduction of the ketones (1) with lithium aluminium hydride gave αβ-unsaturated ketones (2), in which the olefinic (R1) and carbonyl (R2) substituents are reversed compared with the starting αβ-unsaturated ketone (1), or the saturated γ-hydroxy-sulphides (3). Reduction of the ketones (1) with sodium borohydride afforded only the αβ-unsaturated ketones (2). Reduction of (1) with sodium borohydride in the presence of metal halides gave the saturated ketones (5).

Synthesis of Chiral Bis-Thiazolines and Asymmetric Diels–Alder Reactions

Abstract New chiral ligands, bis-thiazoline derivatives (sulfur analogues of known oxazolines) were prepared from chiral bis-(N-acylamino alcohols) with Lawessons reagent. Bis-thiazolines thus obtained proved to be useful chiral ligands for metal in asymmetric Diels–Alder reaction.

Photochemical Reactions of N-(2-Halogenoalkanoyl) Derivatives of Anilines

The photochemical reactions of 2-substituted N-(2-halogenoalkanoyl) derivatives 1 of anilines and 5 of cyclic amines are described. Under irradiation, 2-bromo-2-methylpropananilides 1a – e undergo exclusively dehydrobromination to give N-aryl-2-methylprop-2-enamides (=methacrylanilides) 3a – e (Scheme 1 and Table 1). On irradiation of N-alkyl- and N-phenyl-substituted 2-bromo-2-methylpropananilides 1f – m, cyclization products, i.e. 1,3-dihydro-2H-indol-2-ones (=oxindoles) 2f – m and 3,4-dihydroquinolin-2(1H)-ones (=dihydrocarbostyrils) 4f – m, are obtained, besides 3f – m. On the other hand, irradiation of N-methyl-substituted 2-chloro-2-phenylacetanilides 1o – q and 2-chloroacetanilide 1r gives oxindoles 2o – r as the sole product, but in low yields (Scheme 3 and Table 2). The photocyclization of the corresponding N-phenyl derivatives 1s – v to oxindoles 2s – v proceeds smoothly. A plausible mechanism for the formation of the photoproducts is proposed (Scheme 4). Irradiation of N-(2-halogenoalkanoyl) derivatives of cyclic amines 5a – c yields the cyclization products, i.e. five-membered lactams 6a, b, and/or dehydrohalogenation products 7a, c and their cyclization products 8a, c, depending on the ring size of the amines (Scheme 5 and Table 3).

The photochemical [4+4] cyclodimerization of 2-pyrazinone in the solid state

Abstract Irradiation of 1-methyl-5,6-diphenyl-2-pyrazinone (Ia) in the solid state gave the [4+4] anti dimer (II) in 100% yield, while (Ia) in a solution phase was inert upon irradiation.