坂本 昌巳

Photochemical reactions of nitrogen-containing thiocarbonyl compounds, such as thioamides and thioimides, are reviewed. The thiocarbonyl compounds exhibit high photochemical reactivity for [2+2] photocycloaddtion with alkenes leading to thietanes; this is often followed by ring opening-reaction or rearrangement. Photochemical hydrogen abstraction of thioimides gives lactams and cyclic amines. Some thioamides show activity for cyclization via electron transfer, alpha-cleavage reaction, desulfurization and other miscellaneous reactions. The photochemical reaction of thioamides and thioimides provides not only a new photochemical aspect in the area of organic photochemistry but also a useful synthesis of nitrogen-containing heterocycles.

Photolysis of axially chiral monothiosuccinimides in the presence of diphenylethylene gave spirothietanes effectively, where the cycloaddition took place diastereoselectively by way of the steric effect of the ortho-substituent on the phenyl ring.

The photochemistry of thiocarbonyl compounds has been extensively studied over the past three decades and many new photochemical reactions have been developed. Thiocarbonyl compounds, such as thioketones and thioesters, show considerably high photochemical reactivity toward (2+2)-cycloaddition and hydrogen abstraction by thiocarbonyl sulfur. Simple thioamides are generally inert toward photolysis however, in contrast, cyclic thioamides and arylthioamides show considerable reactivity in a variety of photochemical reactions such as photochemical (2+2)-cycloaddition with various alkenes, and which provides a method for the synthesis of a new C-C bond. The thioimides are more reactive than thioamides toward the photochemical cycloaddition to multiple bonds and hydrogen abstraction by thiocarbonyl sulfur atom. Most thioamides are conveniently prepared by sulfurization of the corresponding amides with thionation reagents such as Lawesson’s reagent or phosphorous pentasulfide. Monothioimides or dithioimides are usually provided by thionation of the corresponding imides with the same thionation reagents or acylation of the corresponding thioamides. The photochemical reaction of thioamides and thioimides provides not only a new photochemical aspect in the area of organic photochemistry but also a useful synthesis of nitrogen-containing heterocycles. Some reviews for thione photochemistry, including thioamides and thioimides, have been reported therefore, the photochemical reactions in this chapter are limited to those developed in the past ten years.

Photoaddition reactions of benzoxazole-2-thiones 1 with cycloalkenes 2 and heteroaromatics 3 were examined. Irradiation of N-acylbenzoxazole-2-thiones 1a and 1b, and 3-(methoxycarbonyl)- and 3-(phenoxycarbonyl)benzoxazole-2(3H)-thiones (1f and 1h, resp.) in the presence of cycloalkenes 2a-2c, cyclohexa-1,4-diene (2d), and indene (2e) yielded 2-substituted benzoxazoles 4-13, 18 and 19, and iminothietanes 14-17, by intramolecular trapping of the acyl or MeOCO and PhOCO groups by thiolate anion of the zwitterionic intermediate I and by the phenolate anion of the zwitterionic intermediate II, respectively, derived from the spirocyclic amino-thietanes AT formed by [2 + 2] cycloaddition of the C=S bond of 1 and C=C bond of 2. Irradiation of 1 in the presence of heteroaromatics 3 gave the 2-substituted benzoxazoles 20-33 exclusively.

Palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate (4) with a dimethyl malonate-BSA-LiOAc system has been successfully carried out in the presence of a new chiral prolinol-derived aminophosphine ligand (3e) in good yield with good enantioselectivity (up to 96% ee).

Irradiation of a benzene solution containing 2-alkoxynicotinic acid esters (0.02 M) and furan (0.2 M) resulted in the formation of cage-type adducts in 73-84% yield. The structure of the adducts was established by X-ray crystallographic analysis. The mechanism involving 4pi+4pi photocycloaddition between the pyridine ring and furan was postulated. Two diastereomeric 4pi+4pi adducts were detected as intermediates in the H-1 NMR spectroscopy, when the solution was irradiated in the presence of diene as a triplet quencher. (C) 2002 Elsevier Science Ltd. All rights reserved.

Irradiation of a benzene solution of 2-alkoxynicotinic acid alkyl esters gave cage-type photodimers in good yields, the structure of which was established by X-ray single-crystal analysis. The maximum quantum yield was 8.0 x 10(-2) when a 5.0 M (almost neat) solution was used. Photolysis of phenyl 2-methoxynicotinate promoted photo-Fries rearrangement to give 1,3- and 1,5-rearranged products. Excimer emission of methyl 2-methoxynicotinate was observed at 77 K.

The photochemical reactions of alkyl and aryl 2-thioxo-3H-benzoxazole-3-carboxylates 1 have been examined. Irradiation of 1 in the presence of tetra- and trisubstituted alkenes 2a and 2b, 2-methylprop-2-ene nitrile 2e, and dienes 2f and 2g gave [2+2] cycloadducts of the C=S bond of 2-thioxobenzoxazoles and the C=C bond of alkenes, spiro[benzoxazole-thietanes] 3, 4, 8-13, 15, 18, 20, 23-26 in moderate-to-good yields. The photoaddition reactions proceed in a regiospecific manner. The spirocyclic compounds obtained are indefinitely stable at room temperature. Irradiation of la in the presence of 1,1- and 1,2-disubstituted alkenes 2c and 2d yielded the products 5-7 of oxazole-ring cleavage. Compound 1d also underwent photoaddition with alkenes to yield spiro[benzoxazole-thietanes] and/or 2-substituted benzoxazoles and/or iminothietanes, depending on the nature of the substituents present in the alkenes. On intramolecular [2 + 2] photoadduct, tetracyclic 27, was obtained, when ethenyl 2-thioxobenzoxazole-3-carboxylate 1e was irradiated.

Palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate 7a using a dimethyl malonate-BSA-LiOAc system has been successfully carried out in the presence of new chiral aminophosphine ligands such as 4 in good yields with good enantioselectivities (up to 96% e.e.). © 2001 Elsevier Science Ltd. All rights reserved.

Palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate (8a) with a dimethyl malonate-BSA-LiOAc system has been successfully carried out in the presence of novel chiral phosphine-oxazinane ligands such as 5b in good yields with good enantioselectivities (up to 95% ee). © 2001 Elsevier Science Ltd.

Palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate 18 with a dimethyl malonate-BSA-LiOAc system has been successfully carried out in the presence of new chiral aminophosphine ligands 1-5 in good yields with good enantioselectivities (up to 85% e.e.). © 2001 Elsevier Science Ltd. All rights reserved.

The reaction of ninhydrin with chlorotrialkylsilane gave a silylated ninhydrin dimer accompanied with bis(trialkylsilyloxy) derivatives; the dimeric structure was established by X-ray crystallographic analysis. The dimer is soluble in a nonpolar solvent and easily reproduces ninhydrin under mild conditions; thus it can be used as an equivalent molecule of ninhydrin for utilization as a detecting reagent. (C) 2001 Elsevier Science Ltd. All rights reserved.

Palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate (4) with a dimethyl malonate-BSA-LiOAc system and its derivatives has been successfully carried out in the presence of a new chiral hydrazone ligands such as 2-(diphenylphosphino)benzaldehyde SAMP hydrazone (DPPBA-SAMP) (3a) in high yields with high enantioselectives.

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.

Cyclization of terpenic 3-hydroxy acids in the presence of a catalytic amount of iodine gave bicyclic or tricyclic lactones in good yield.

Various optically active 1,4-aminoalcohols were synthesized from (+)-camphor and (-)-fenchone. The aminoalcohols 5 or 6-mediated enantioselective addition reactions of diethylzinc to benzaldehyde resulted in the formation of the optically active secondary alcohol in good yield. When the catalyst derived from (+)-camphor was used, the (S)-alcohol was obtained in high ee, while the (R)-alcohol was obtained in the reaction with the catalyst derived from (-)-fenchone. Copyright (C) 2000 Elsevier Science Ltd.

The photochemical reaction of 1-cyanonaphthalene (1-CNNap) with substituted pyridine was studied. Irradiation of a benzene solution of 1-CNNap (0.02 M) in the presence of 3-cyano-2-methoxypyridine (0.02 M) gave a 1:1 adduct in 24% yield and the pyridine dimer in 56% yield, when the reaction conversion reached 32%. Photoaddition of 1-CNNap with 3-cyano-2-methoxy-6-methylpyridine, 3-cyano-4,6-dimethyl-2-methoxypyridine, or 3-cyano-2,6-dimethoxypyridine was also successful, and the corresponding adducts were isolated in 41%, 75%, and 98% yield, respectively. The structure was established by X-ray structural analysis. The postulated mechanism initiated by 2 pi+2 pi photocycloaddition between the C3-C4 position of 1-CNNap and the C2-C3 position of the pyridine was supported by Frontier-MO calculations using the PM3 Hamiltonian contained within the MOPAC program. The naphthalene-pyridine adducts were stable at room temperature; however, pyrolysis of the adduct gave a 1,3-sigmatropic rearrangement product, quantitatively.

Enantioselective addition reactions of diethylzinc to aldehydes were performed by catalytic reactions with chiral 1,4-aminoalcohols. Optically active 1,4-aminoalcohols were synthesized from (+)-camphor and (-)-fenchone through four steps involving iodine-mediated lactonization of 3-hydroxy acids. (C) 2000 Elsevier Science Ltd.

Palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2- propenyl acetate (8) with a dimethyl malonate-BSA-LiOAc system has been successfully carried out in the presence of new chiral P,N-ligands 5 in good yields with good enantioselectives (up to 83% ee).

Enatioselective additions of diethylzinc to aldehydes were demonstrated, and good to moderate enantioselectivities (54 to 95% enantiomeric excess) were obtained. The ligand 4 was prepared from camphor and acetic acid in a facile process of four steps, and the chiral source was only inexpensive (+)- camphor. (C) 2000 Elsevier Science Ltd.

Irradiation of a benzene solution containing 3-cyano-2-methoxypyridine (0.02 M) and benzofuran (0.5 M) resulted in the formation of stereo-isomeric 1:1 adducts, endo and exo-7-cyano-2-methoxy-4-methyl-9-oxa-3-aza-10,11-benzotricyclo[6.3.0.0(4,7)]undeca-2,5-diene, accompanied by 5-cyano-2-methoxypyridine and a pyridine dimer; the structures of the adducts were established by X-ray structural analyses.

Photochemical reaction of asymmetrically substituted N-benzyl-N-methylmethacrylthioamide both in solution and in the solid state was investigated. The thioamide exists in an equilibrium between two rotamers owing to rotation about the C(=S)-N bond. The free energy of activation for the bond rotation was estimated as 22.7 kcal mol(-1) by temperature-dependent H-1 NMR spectroscopy. The thioamide crystallized in a chiral fashion, and the photoreaction in the solid state gave the optically active beta-thiolactam whereas both the beta-thiolactam and the corresponding thiazolidinethione were obtained by solution-phase photochemistry.

The photochemical reaction of the bis-aromatic system pyridine-furan was investigated. Irradiation of a benzene solution containing 3-cyano-2-methoxypyridines 1 (0.02 M) and furan (0.2 M) resulted in the formation of a 1:1 adduct, 11-cyano-10-methoxy-8-methyl-4-oxa-9-azapentacyclo[5.4.0.0(2,6).0(3,11).0(5,8)]undec-9-ene and 10-cyano-9-methoxy-7-methyl-5-oxa-8-azatricyclo[5.4.0.0(2,6)]undeca-3,8,10-triene in 30 and 16% yield, accompanied by the transpositional pyridine, 5-cyano-2-methoxy-6-methylpyridine, and the pyridine dimer, in 2 and 44% yield, respectively, when the reaction conversion reached 48% yield. The cage and the face-to-face structures were established by X-ray structural analyses. The cage adduct was stable under neutral conditions; however, it easily converted to a face-to-face structure in acidic conditions. On the other hand, though the face-to-face structure was stable at rt, the starting pyridine 1 and furan were easily regenerated quantitatively by heating (>100 degrees C) or irradiation (>290 nm). The 4 + 4 adduct of pyridine with furan was detected by H-1 NMR spectroscopy, and subsequently transformed to a cage structure on irradiation.

3, 4-不飽和酸と飽和あるいは不飽和グリニヤール試薬との反応による長鎖のケトン合成について検討した。例えば, (E) -3-ヘキセン酸エチル (1b) とn-アミルプロミド (2a) とのグリニヤール反応により, 3-ドデセン-6-オン (3b) と6-n-アミル-3-ドデセン-6-オール (5b) が得られた。トリエチルアミン存在下, 253Kで反応を行ったところ, ケトンの選択性向上が見られた。他の3, 4-不飽和酸エステル (1b-d) または不飽和酸 (1a', b'c') とグリニヤール試薬 (2a-c) との反応でも, 同じ条件下でケトン体 (3b, c, d, f) が高収率で得られた。<BR>これらの反応で副生したジアルキルモノホモアリルアルコール (5b, f-i) は熱分解によって対称的なケトン (6b, f-i) に変換できた。一方, トリホモアリルアルコール (5q, r, t) を用いたときは, ジアリルケトン (3q, r, t) が得られた。これらのケトンは酸触媒と作用させると容易に共役ケトン (7q, t) へ異性化した。以上の反応を応用して, 共役ケトンにグリニヤール試薬を1, 4-付加させることにより, ar-ツルメロンを始めとする種々の不飽和ケトンを選択的に合成した。

Solid-state photoreactions of S-(o-tolyl), S-phenyl, and S-(m-tolyl) 2-benzoylbenzothioates, which formed chiral crystals by spontaneous resolution, underwent an unprecedented intramolecular cyclization involving phenyl migration to afford optically active corresponding 3-phenyl-3-(arylthio)phthalide in good chemo- and enantioselectivities. Stereochemical assignment and substituent probe experiment of this photoreaction sequence led to a reliable conclusion that this reaction was rationalized on the basis of the aryl migration rather than the well-recognized radicalic mechanism. Furthermore, the chirality preservation in the crystals was demonstrated by means of the bisignated CD spectra, which allowed assignment of the origin of the specific CD band and the helicity of the chiral molecules.

Photochemical reactions of S-aryl 2-benzoylbenzothioates 1 in solution media have been investigated, These thioesters undergo photoinduced cyclization to 3-aryl-3-arylthioisobenzofuranones 2 in yields of 14-46% upon direct irradiation. The photocyclization reaction is accompanied by a subsequent homolytic cleavage reaction of the isobenzofuranone leading to the dihydroisobenzofuranone dimer, (+/-)- and meso-3,3'-dioxo-1,1'-diphenyl-1,1',3,3'-tetrahydro-1,1'-bi(isobenzofuranyl) 5. The formation of the dihydroisobenzofuranone 2 can be explained by a stepwise mechanism involving (i) intramolecular cyclization to a zwitterionic intermediate and (ii) subsequent aryl migration. Furthermore, sensitization and quenching studies reveal that the photochemical process occurs from the singlet excited states of the thioesters 1.

A series of esters was prepared from the reaction of acid chlorides with polymeric nonionic surface-active agents (copolymer of propylene oxide and ethylene oxide), and they were screened for antirust and other properties associated with water-based cutting fluids. An aqueous emulsion of an adduct of triethanolamine and the oleic acid ester of polymeric nonionic surface-active agent showed excellent antirust properties when used as a water-based cutting fluid. The emulsion of triethanolamine and the mono nonyl ether of the surface-active agent also showed antirust properties.

プロピレンオキシドとエチレンオキシドのコポリマー (CPO) と酸塩化物の反応によって, エステル類を合成した。水溶性切削液としてのさび止め性と他の性能を評価した。CPOのオレイン酸エステルとトリエタノールアミンの水溶液は水溶性切削液として非常に高いさび止め性を示した。

Pd(PPh3)4 catalyzed reaction of linalyl acetate with diethylamine gave N, N-diethylgeranylamine as a main product (E:Z = 90:10). The reaction of linalyl acetate with various amines gave their corresponding products. For example, the reaction of aniline with linalyl acetate gave N-geranylaniline in 100% stereoselectivity. The reaction of linalyl methylcarbonate with diethylamine using a Pd(0) catalyst similarly gave N, N-diethylgeranylamine (E:Z = 92:8). © 1997, Taylor &amp Francis Group, LLC. All rights reserved.

アミノ酸と酸塩化物の反応で多数の賦課物を合成し, 水溶性切削油剤としての性能を検討した。N-アシルロイシン, N-アシルグルタミン酸などのトリエタノールアミン塩の水溶液は水溶性切削剤油剤としてすぐれたさび止め性と耐荷重能を示した。

The photochemical cycloaddition of 2-alkoxy-3-cyano-4,6-dimethylpyridine with methacrylonitrile gives a bicyclic azetine, 6-alkoxy-3,5-dicyano-2,5,8-trimethyl-7-azabicyclo[4.2.0]octa-2,7-diene (45-55% yield) and 3-acetyl-4-amino-1,5-dicyano-2,5-dimethylcyclohexa-1,3-diene (15-17% yield).

Rearrangement of linalyl acetate with PdCl2(PhCN)2 gave geranyl acetate as a main product(E:Z=86:14). A solution of linalyl acetoacetate in tetrahydrofuran was stirred at room temperature in the presence of Pd (PPh3)4 to give geranylacetone, E: Z = 93:7. © 1996, Taylor &amp Francis Group, LLC. All rights reserved.

アダマンタンカルボニルクロリイド (I) とアミノアルコール, アミノ酸の反応で多数の付加物を合成し, 水溶性切削油剤としての性能を検討した。N- (1-アダマンタンカルボニル) -O- (1-アダマンタンカルボニル) モノエタノールアミン (III) の水溶液は水溶性切削油剤として優れた防錆性と抗菌性を示した。

The photochemistry of O-allyl and O-but-3-enyl thiocarbamates has been studied. Photolysis of benzene solutions of O-allyl N-phenylthiocarbamates gave S-allyl N-phenylthiocarbamates. The 1,3-allyl migration from the oxygen to the sulfur involves a concerted process. The same type of 1,3-migration took place in the conversion of O-benzyl N-phenylthiocarbamate into S-benzyl N-phenylthiocarbamate. Irradiation of O-but-3-enylthiocarbamates produced iminooxolanes via aminothietane intermediates. In the case of O-but-3-enyl N-benzoyl-N-phenylthiocarbamates. 3-(benzoylsulfanylmethyl)-2-phenyliminooxolanes were obtained via a ring opening of the aminothietanes involving a 1,5-benzoyl shift.