三野 孝

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 substitution of 1,3-diphenyl-2-propenyl acetate (3) with a dimethyl malonate-BSA-lithium acetate system has been successfully carried out in the presence of chiral ferrocene hydrazone such as (S)-alpha-(diphenylphosphino)ferrocenecarboxaldehyde SAMP hydrazone (DPPFA-SAMP) ((S,S)-2a) in high yields with high enantioselectives (up to 96% ee).

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.

Palladium-catalysed 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 new chiral phosphine amide, such as 5, in good yields and high enantiomeric excesses of up to 85%. (C) 2001 Elsevier Science Ltd. All rights reserved.

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. (C) 2000 Elsevier Science Ltd. All rights reserved.

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.

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).

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 foul steps involving iodine-mediated lactonization of 3-hydroxy acids. (C) 2000 Elsevier Science Ltd. All rights reserved.

Enantioselective 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. All rights reserved.

Deprotection of ketone dimethylhydrazone compounds with porcine pancreatic lipase (PPL) as a biocatalyst is described. (C) 2000 Elsevier Science Ltd. All rights reserved.

Several types of achiral N,N-dibenzyl-α,β-unsaturated thioamides were subjected to X-ray crystallographic analysis, and it was revealed that methylcrotonthioamide and 1-cyclohexenecarbothioamide provided chiral crystals. The absolute configuration determined by anomalous scattering method corresponded to the cotton effect in the solid-state CD spectra. The solid-state photoreaction gave optically active β-thiolactams. On the other hand, E-Z isomerization takes place in the photoreaction of a tiglylthioamide derivative. Stereochemical assignment before and after the reaction was rationalized by the hydrogen abstraction by alkenyl carbon followed by cyclization via a zwitterionic intermediate. (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.

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-metho.\y-8-methyl-4-oxa-9-azapentacyclo[5.4.0.02,6.03,11O5,8]undec-9-ene and 10-cyano-9-methoxy-7-methyl-5-oxa-8-azatricyclo[5.4.0.02,6]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 °C) or irradiation (>290 nm). The 4 + 4 adduct of pyridine with furan was detected by1H 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。

Hydrazones of ketones and aldehydes undergo facile cleavage to the corresponding carbonyl compounds by a catalytic amount of Pd(OAc)2/SnCl2 in good yields.

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.

O-Methyl N-(2,2-dimethylbut-3-enoyl)-N-phenylthiocarbamate crystallized in the chiral space group P2(1), and the solid state photoreaction initiated intramolecular [2+2] thietane formation followed by rearrangement, leading to optically active gamma-thiolactone.

Photochemical reaction of asymmetrically substituted N-benzyl-N-isopropyl-alpha,beta-unsaturated thioamides both in solution and in the solid state was investigated. All thioamides exist in an equilibrium between two rotamers owing to the rotation of the C(=S)-N bond. The free energy of activation for the bond rotation was estimated by temperature-dependent H-1 NMR spectroscopy. The free energy of activation lies in a range 18.4-19.5 kcal mol(-1). Irradiation in benzene solution proceeded to give hydrogen abstraction by alkenyl carbon from both benzyl and isopropyl groups, leading to beta-thiolactam and 1,3,5-dithiazinane products, respectively. Hydrogen abstraction from only the isopropyl group took place in the solid-state photolysis, giving an isomeric beta-thiolactam product.

O-Methyl N-(2,2-dimethylbut-3-enoyl)-N-phenylthiocarbamate crystallized in the chiral space group P21, and the solid state photoreaction initiated intramolecular [2+2] thietane formation followed by rearrangement, leading to optically active γ-thiolactone.

Photochemical reaction of asymmetrically substituted N-benzyl-N-isopropyl-α,β-unsaturated thioamides both in solution and in the solid state was investigated. All thioamides exist in an equilibrium between two rotamers owing to the rotation of the C(=S)-N bond. The free energy of activation for the bond rotation was estimated by temperature-dependent1H NMR spectroscopy. The free energy of activation lies in a range 18.4-19.5 kcal mol-1. Irradiation in benzene solution proceeded to give hydrogen abstraction by alkenyl carbon from both benzyl and isopropyl groups, leading to β-thiolactam and 1,3,5-dithiazinane products, respectively. Hydrogen abstraction from only the isopropyl group took place in the solid-state photolysis, giving an isomeric β-thiolactam product.

The use of chiral imines 1-4 prepared from (4S,5S)-(+)-5-amino-2,2-dimethyl-4-phenyl-1,3-dioxane (ADPD) in the enantioselective addition of diethylzinc to aryl aldehydes is reported. Secondary aryl alcohols are obtained up to 85% ee in good yields.

(S)-2-Alkyl-2-methyl-3-butenals that have a quaternary stereogenic carbon atom at the α-position were obtained from 2-methyl-2-butenal (4S,5S)-ADPD-imine in good enantioselective excesses (up to 81% ee). Using this reaction, a novel sesquiterpene, (+)-(E)-2,5,9-trimethyl-2-vinyl-4,8-decadienal, was synthesized with moderate enantioselectivity (53% ee).

α-Phenyl ketone 4 was obtained from N,N-dimethylhydrazone 1 by arylation with (π-chlorobenzene)chromium tricarbonyl in good yield.

Palladium-catalyzed asymmetric allylic substitution of 1,3-diphenyl-2- propenyl acetate (3) with a dimethyl malonate-BSA-LiOAc system and its derivatives has been successfully carried out in the presence of a new chiral hydrazone ligand 2-diphenylphosphinobenzaldehyde SAMP hydrazone (DPPB-SAMP) (2) in high yields with high enantioselectives (up to 92% ee).

2-Alkyl-2-methyl-3-butenenitriles which have an asymmetric quaternary carbon atom at the a-position were obtained from 2-methyl-2-butenal SAMP hydrazone in good enantiomeric excesses (e.e. = 73-95 %). This shows that diasteroselective alkylation occurred at the a-position and the a,b-unsaturated double bond migrated to b,g. The absolute configuration of 2-benzyl-2-methyl-3-butenenitrile was determined as R by derivatization and comparison of optical rotation.

Ketone dimethylhydrazones 1 undergo facile cleavage to the corresponding ketones 2 by a catalytic amount of Pd(OAc)2 / SnCl2 in good yields.