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Three procedures for the allylation of acetals and aminals with (Z)-1-trimethylsilylalkenes are elaborated: direct allylation, three-component reaction of the respective aldehyde, orthoformate or carbamate, and silylalkene, and pretreatment of the silylalkene followed by addition of acetal or aminal.

Z-Alkenylsilanes are used as γ-substituted allylsilane precursors for the allylation of carbon electrophiles such as aryl and alkyl acetals and aminals which may be synthesized in situ from the corresponding aldehyde and ortho-formate or methyl carbamate, respectively.

A new catalytic system for the metathesis-type coupling of alkynes (I) and aldehydes (II) is developed.

N-Bis(methylthio)methylene-p-toluenesulfonamide (1) reacted with active methylene compounds such as malononitrile (2a) and, cyanoacetamide (2b) to give the corresponding 3-methylthio-3-p-toluenesulfonylami-nopropenenitrile derivatives 3a,b which were found to be convenient starting materials for the synthesis of 3,5-diaminopyrazole derivatives. Reaction of 3a and 3b with hydrazines gave the corresponding 3,5-diaminopyrazoles 4a-e, key intermediates for the synthesis of 3-aminopyrazolo[3,4-d]pyrimidine derivatives 5a-d.

2-Aminomethyl-1,3-butadienes and 2,3-bis(aminomethyl)-1,3-butadienes, readily prepared by the Grignard cross-coupling reaction of 2-bromo-2-aminopropene and vinylic bromides, are good Diels–Alder dienes toward various activated dienophiles to afford aminomethyl-substituted cyclohexenes.

Methyl 3-(N-arylamino)-2-cyano-3-methylthioacrylates 3a-h, which are readily prepared by the reaction of the ketene dithioacetal, methyl 2-cyano-3,3-bis(methylthio)acrylate (1) with arylamines, was heated at reflux in diphenyl ether to give the corresponding 2-methylthio-4-hydroxyquinoline-3-carbonitriles 4a-h in 14–77% yields. The reaction of 1 with excess aryl amines in diphenyl ether at reflux gave also the corresponding 2-arylamino-4-hydroxyquinoline-3-carbonitriles 6a-d. The 2-methylthioquinoline-3-carbonitriles 4a-h, thus obtained, are useful intermediates for the synthesis of various quinoline derivatives.

Substituted imidazoles was ozonolyzed cleanly without any complicated procedures into the corresponding N-acylamides, which were regarded to be much useful derivatives of either amines or acyl compounds

2-Trimethylsilylethyl-1,3-butadiene, readily prepared by the cross-coupling reaction of the Grignard reagent of 3-bromo-3-butenyltrimethylsilane with vinyl bromide catalyzed by a nickel-phosphine complex, works as a synthetic equivalent to 3-methylene-1,4-pentadiene (parent [3]dendralene) by the consecutive Diels-Alder reactions.

Titanium dialkylamide, readily available, adds to a α,β-unsaturated esters and ketones in a conjugate addition mode to give ester and ketone enolates, respectively, which are successively quenched with electrophiles such as aldehydes and acetals. The aldol products can be readily converted to the corresponding deaminated or dehydrated derivatives selectively.

Various organosilicon compounds act as synthetic equivalents of unstable active chemical species, especially novel 1, 3-dipolar reagents such as azomethine ylides, thiocarbonyl ylides and related reagents, are designed and synthesized. These compounds activated by a Lewis acid or fluoride ion react with a variety of dipolarophiles and hetero-dipolarophiles in highly regio- and stereospecific mode. It has been found that this methodology can be extended to the design and preparations of tailor-made 1, 3-dipolar reagents. The highly selective synthesis of heterocycles are described.

Irradiation of 4-(dialkylamino)-2-aryl-1-butenes gave cyclization prodcuts, 3-methyl-3-arylpyrrolidines, in high yields. These styrylamines formed fluorescent intramolecular exciplexes, but studies based on Stern-Volmer quenching for the fluorescence and the photoreaction suggested that the emissive exciplexes did not participate in the photoreaction

4-Substituted 1-acetylimidazoles (6), which were derived from 4(5)-substituted imidazoles (1), were N-alkylated by the treatment with alkyl halides. During the work-up, the resulting N-alkylated products were easily hydrolyzed into 1,5-disubstituted imidazoles (3). These reactions were regarded to be the general method for the preparation of sterically more crowded 1,5-disubstituted imidazoles (3)

According to four different methods, various types of N-acylpyrazoles were prepared from the corresponding pyrazoles and carboxylic acids or their acid chlorides. Although N-acylpyrazoles were inert to alcohols under neutral or weakly basic conditions, the alcoholysis was dramatically accelerated by the action of strong acid or base. On the basis of these chemical properties, the regioselective synthesis of methyl benzyl 2,2-dimethylglutarate was achieved by selective protection and functionalization of a carboxylic acid derivative using N-acylpyrazoles

As a new chiral auxiliary compound having a pyrazole ring system, the synthetic utility of (4R,7S)-3-phenyl-4-methyl-7-isopropyl-4,5,6,7-tetrahydroindazole (3-phenyl-l-menthopyrazole), which was prepared from l-menthone, was discussed.

Ketene dithioacetals bearing an alkoxycarbonyl group at 2-position are effectively reduced by two equimolar amounts of dimethylcuprate derived from methyllithium and cuprous cyanide to yield the corresponding functionalized vinylcopper species. These organocopper species are efficiently trapped by carbon electrophiles. Formal substitution reactions of a methylthio group in ketene dithioacetals by electrophiles can be attained by one-pot operation. Synthesis of β-thiobutenolides was also achieved.

photochemical reaction of 4-thioxoazetidine-2-one with alkenes gave [2+2] adducts (thietane-fused b-lactams which were converted to 4-spirocyclopropyl b-lactams on desulfurization with Raney nickel.

The photochemical reactions of benzothiazole-2-thiones in the presence of alkenes have been examined. Irradiation of N-unsubstituted benzothiazole-2-thione in the presence of electron-poor alkenes gave 2-substituted benzothiazoles. Irradiation of N-substituted benzothiazole-2-thiones and electron-poor alkenes yielded 2-alkylidenebenzothiazoles and the unexpected spiro-1,3-dithianes. The formation of these photoproducts can be explained in terms of the intermediacy of aminospirothietanes, which are derived by [2 + 2] photocycloaddition of the CS bond of benzothiazole-2-thiones to the CC bond of alkenes.

The photocycloaddition of benzothiazole-2-thiones to electron-rich and aryl-substituted alkenes are described. Irradiation of N-unsubstituted benzothiazole-2-thione (1) in the presence of alkenes 3 gave 2-(2′-mercaptoalkyl)benzothiazoles 4, and 2-substituted benzothiazoles 5 and 6 (in the case of 3a and 3h, resp.) through the ring cleavage of an intermediate 2-aminothietane (Schemes 1 and 3). The latter was formed by [2+2] cycloaddition of the CS bond of 1 and the CC bond of 3. Irradiation of N-methylbenzothiazole-2-thione (2) and 2-methylpropene (3a) gave the spiro-1,3-dithiane 8, 1,2,6-benzodithiazocin-5-one 9, and disulfide 10. The structure of 9 was established by X-ray crystal-structure analysis.

Sulfur-substituted allylcopper species, generated by a novel reduction reaction of ketene dithoacetals bearing a chlorine atom at an allylic position using organocuprate, react with aldehyde, ketone, chlorotrimethylsilane, enone, oxirane and ester to afford the corresponding allylated products.

Functionalized (E)-vinylcopper species, selectively generated by the effective reduction of cyanoketene dithioacetals with two equimolar amounts of cuprates, react with electrophiles such as water, allyl bromide, and acid chlorides to give the corresponding substitution products in good yields.

Vinyl radicals, generated from the reaction of vinyl iodides with tributylstannyl radical, react with electron-deficient alkenes to give di- or trisubstituted alkenes in moderate to good yields. The stereoselectivity is largely dependent on the substituent at 1- and 2-position of vinyl iodides.

The conversion of N-acylpyrazoles into β-keto esters was accomplished efficiently by the treatment with α-bromo esters and zinc dust. Using this Reformatsky reaction of N-acylpyrazoles, 4-(protected amino)-3-oxoalkanoic acid derivatives were conveniently prepared as the key intermediates in the synthesis of statines.

The photochemical reactions of the benzoxazole-2-thiones 6 have been examined. Irradiation of 3-unsubstituted benzoxazole-2-thione 6a in the presence of alkenes 2 gave 2-alkylated benzoxazoles 7, 9–15 and 8 (in the case of 2a). Irradiation of 3-substituted benzoxazole-2-thiones 6b–e and acrylonitrile 2f yielded the 2-alkylidenebenzoxazoles 17, 22 and 24–25. Irradiation of 6b–e in the presence of 1,1-di-and tetra-substituted alkenes 2a,c and e gave the amide derivatives 18–20, 23 and 26. The 3-(alk-ω-enyl)-benzoxazole-2-thiones 6g–i gave the lactam derivatives 28g–i upon irradiation. The formation of these photoproducts can be explained in terms of the intermediacy of amino spiro-thietanes, which are derived by [2 + 2] photocycloaddition of the CS bond of benzoxazole-2-thiones and the CC bond of alkenes.

After deprotonation with LDA, 2-acyl-3-phenyl-l-menthopyrazoles (13) were diastereomerically α-acylated to give N-(3-phenyl-l-menthopyrazolyl) β-keto amides (14–19). The subsequent amides were converted into the corresponding N-alkyl amides (21–24) retaining their enantiomeric enrichment on the α-position. These are the first examples of enolizable β-keto acid derivatives having only one chiral center at α-position. These chiral β-keto amides were surprisingly stable in dry benzene and their optical asymmetries were almost retained for two weeks at room temperature without any epimerization.

“Tailor-made” carbonyl ylides bearing only alkyl substituents or no substituents were efficiently generated from α-chloroalkyl α′-chloroalkyl ethers in the presence of samarium reagents. Using these novel and synthetically practical carbonyl ylides, optionally substituted and stereochemically defined tetrahydrofurans, dihydrofurans and dioxolane were synthesized in a single step.