坂本 昌巳

Palladium-catalyzed Mizoroki-Heck reaction of allyl aryl ethers with aryl iodides gave aryl cinnamyl ethers using a catalytic amount of Pd(OAc)2 in DMF at 50 °C with phosphine-free hydrazone as a ligand in good yields. © 2009 Elsevier Ltd. All rights reserved.

A new atropisomeric dihydrobenzofuran-based bisphosphine ligand 1 was easily prepared from 1,4-dibromo-2-fluorobenzene. This racemic bisphosphine (±)-1 was used as a ligand for the palladium-catalyzed Suzuki-Miyaura reaction of aryl chloride with arylboronic acids and Hartwig-Buchwald amination of aryl bromides with aniline derivatives. The optical resolution of (±)-1 was also carried out by HPLC with a chiral stationary phase column. © 2009 Elsevier Ltd. All rights reserved.

Intramolecular etherification of 1,3-diols was investigated using iodine as a catalyst under solvent-free conditions. The reaction proceeded to completion in a heterogeneous system. Five-membered cyclic ethers were obtained by intramolecular cyclization of 1,3-diols with dehydration. A propella ether (11-oxatricyclo[4.4.3.01,6]tridecane) was conveniently synthesized from a 1,3-diol (6-(2-hydroxyethyl)spiro[4.5]decan-6-ol) in 86% yield with carbon skeleton rearrangement under the following conditions: a temperature of 60°C, a molar ratio of 1,3-diol:iodine = 1:0.2, and a time period of 3 h. Bicyclic ethers were also obtained from the corresponding 1,3-diols, but spiro ethers were obtained in lower yield. Terpenic cyclic ethers were efficiently synthesized from the corresponding 1,3-diols, derived from (+)- camphor and (-)-fenchone. In the case of etherification with a mechanism of carbon skeleton rearrangement, the yield of the solvent-free reaction was as high as that of the corresponding reaction in solution. Etherification reactions with carbon skeleton rearrangement proceeded more smoothly than those with hydride shift. © 2009 by Japan Oil Chemists' Society.

Irradiation of the simple chromone (benzo-γ-pyrone) resulted in the formation of two types of dimers, anti-HT (head-to-tail) and trans-fused HT isomers, whose structures were established by X-ray structural analysis. © The Royal Society of Chemistry 2009.

Copper-catalyzed C-C coupling reaction of aryl iodides with diethylmalonate in toluene at 90C gave arylated malonates using 5 mol% of CuI with hydrazone 1a as a ligand in good yields under an aerobic atmosphere. We also found CuI/hydrazone 1b in toluene to be an efficient catalytic system for C-O coupling reactions of aryl bromides with phenols to give aryl ethers in good yields at 110C under an aerobic atmosphere.

Chiral allylic esters, such as (R)-1,3-diphenyl-2-propenyl acetate (R)-2a, were synthesized by kinetic resolution in a palladium-catalyzed asymmetric allylic alkylation using N-aryl indoline type C-N bond axially chiral aminophosphines (S)-1 as ligands. © 2008 Elsevier Ltd. All rights reserved.

Palladium-catalyzed allyl cross-coupling reaction of allylic acetates with a variety of boronic acids at room temperature using a catalytic amount of Pd(OAc)2 with phosphine-free hydrazone as a ligand gave the allylbenzene derivatives in good yields.

Phosphine-free hydrazone such as 1c was found to be an efficient ligand for the copper-catalyzed Goldberg-type N-arylation of amides and Ullmann-type N-arylation of azoles with aryl halides under mild conditions. A variety of N-arylamides and N-arylazoles were synthesized in good to high yields. © Georg Thieme Verlag Stuttgart.

A photosensitized reaction was performed using molecular chirality, which was generated and amplified by the spontaneous crystallization of achiral coumarincarboxamide. The molecular chirality was retained in a cold solution caused by slow racemization and was transferred to optically active products by a photosensitized 2 + 2 cycloaddition reaction with high enantiomeric excesses. Copyright © 2008 American Chemical Society.

Intramolecular cyclic etherification of 1,3-diols was investigated using iodine as a catalyst under solution reaction conditions. Compounds containing five-membered ether rings were obtained. Propella ether (11-oxatricyclo[4.4.3.01,6]tridecane) was conveniently synthesized from 1,3-diol (6-(2-hydroxyethyl)spiro[4.5]decan-6-ol) in 97% yield via carbon skeleton rearrangement. Spiroethers and bicyclic ethers were also obtained from the corresponding 1,3-diols in yields of over 77%. The most suitable reaction conditions were a temperature of 80°C, a 1:0.2 molar ratio of 1,3-diol:iodine, and a time period of 8 h. In addition, terpenoic ethers were efficiently synthesized from the corresponding 1,3-diols, derived from (+)-camphor and (-)-fenchone, via skeleton rearrangement. In particular, the reaction of the 1,3-diol derived from (+)-camphor proceeded smoothly at room temperature with a yield of 91%. The yield of the cyclic ether using iodine as a catalyst was comparable to the method using sulfuric acid. Copyright ©2008 by Japan Oil Chemists' Society.

Optically active β-lactams were synthesized via photochemical intramolecular γ-hydrogen abstraction reaction of thioimides involving a highly-controlled chiral-memory effect. © The Royal Society of Chemistry.

2-Quinolone-4-carboxamide derived from (S)-proline, which exists as a mixture of two diastereomers before crystallization, converged to a single diastereomer by crystallization (CIDT), and the homochirality was transferred by a intermolecular 2 + 2 photocycloaddition reaction with high optical activity. © The Royal Society of Chemistry.

N-Phenyldiethanolamine (1f) is an efficient ligand for zinc-catalyzed transesterification of alcohols with vinyl acetate (R3 = Me) at room temperature. In the case of using other vinyl esters (R3 = Et, n-Pr, Ph), the corresponding products were easily obtained in the presence of pyridine-type ligand 2 instead of aminoalcohol 1f. © 2007 Elsevier B.V. All rights reserved.

Naphthamides derived from L-proline, which exist as a mixture of several diastereomers in solution, converged to single diastereomer by crystallization, and the conformational transformation was controlled after the crystals were dissolved in the solvent at low temperature, where the frozen conformation was retained long enough for subsequent asymmetric reaction. © The Royal Society of Chemistry.

An asymmetric SNAr reaction was performed by using molecular chirality generated and amplified by the spontaneous crystallization of achiral naphthamides the chirality was retained in a cold solution, caused by slow racemization, and was transferred to stable axially chiral materials with high enantiomeric excesses. © The Royal Society of Chemistry.

Intramolecular cyclization of 3-hydroxy acids was investigated using iodine as a catalyst under solvent-free conditions. The reaction proceeded to completion in the heterogeneous system. Lactones were obtained by intramolecular cyclization of 3-hydroxy acids. Propella lactone (11-oxatricyclo[4.4.3.0(1,6)]tridecan-12-one) was conveniently synthesized from 3-hydroxy acid ((6-hydroxyspiro[4.5]dec-6-yl)acetic acid) in 88% yield with carbon skeleton rearrangement. Spiro lactones and bicyclic lactones were also obtained from the corresponding 3-hydroxy acids in yields of over 75%. The most suitable reaction conditions were a temperature of 80 degrees C, a molar ratio of 3-hydroxy acid:iodine = 1:0.1, and a time period of 6 h. In addition, terpenic lactones were efficiently synthesized from the corresponding 3-hydroxy acids, derived from (+)-camphor, (-)-fencone, and (-)-pulegone, with skeleton rearrangement. The yield of the solvent-free reaction was as high as that of the corresponding reaction in solution.

(Chemical Equation Presented) Palladium/copper-catalyzed Sonogashira cross-coupling reaction of aryl halides with a variety of terminal alkynes under amine-free conditions in dimethylformamide (DMF) at 80 °C gave internal arylated alkynes using PdCl2(MeCN)2 with phosphine-free hydrazone 2a as a ligand and CuI as the cocatalyst in good yields. We also found PdCl2/hydrazone ligand 1d in PhMe at 80°C was a phosphine-free efficient catalyst system for a Hiyama cross-coupling reaction of aryl bromides with aryl(trialkoxy)silanes in good yields. © 2006 American Chemical Society.

Asymmetric transformation using chiral crystals which are derived from chiral crystallization of achiral materials has been summarized. Solid-state photoreaction in the chiral crystal environment provides the reproducible absolute asymmetric synthesis via the cycloaddition reaction, hydrogen abstraction reaction, di-Tr-methane rearrangement, electrocyclization, and the bond-cleavage reaction. Furthermore, asymmetric syntheses using chiral crystals except solid-state photoreactions such as solid-gas reaction, catalytic asymmetric automultiplication, and the reaction in homogeneous conditions are also reviewed. (c) 2007 Elsevier B.V. All rights reserved.

Optically active hydrazone and imine were found to act as effective ligands for enantioselective addition of diethylzinc to aldehydes. This reaction provided optically active secondary alcohols with ee up to 71%. © 2006 Elsevier B.V. All rights reserved.

N-Aryl indoline-type aminophosphines 1a-c were obtained in good yields by a nucleophilic aromatic substitution (SNAr) reaction followed by silane reduction. Aminophosphine 1d was also prepared from 2,3- difluorobenzaldehyde (4) via dimethylhydrazone. Optical resolution of C(aryl)-N(amine) bond atropisomers was achieved using (5)-(+)-di-μ- chlorobis[2-[(dimethylamino)ethyl]phenyl-C2,N]dipalladium-(II) ((S)-10). The determination of absolute configuration and the investigation of the rotation barrier for C(aryl)-N(amine) bond axial stability of an aminophosphine 1 are described. Finally, the ability of the chiral phosphine ligand 1 is demonstrated in a catalytic asymmetric reaction, such as a palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate (up to 95% ee). © 2006 American Chemical Society.

Glyoxal bishydrazones 1 and pyridyl-hydrazone 2b were prepared and examined as a ligand for the Mizoroki-Heck cross-coupling reaction of aryl halides and olefin. We found that PdCl2(MeCN)2/hydrazone ligand 1e was a phosphine-free efficient catalyst system for a variety of substrates to produce the Mizoroki-Heck coupling products in good yields. © 2006 American Chemical Society.

Palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate (5) with a dimethyl malonate-BSA-LiOAc system has been successfully carried out in the presence of chiral pyridyl-hydrazone ligands such as 2c with moderate enantioselectivities (up to 67% ee). © 2006 The Japan Institute of Heterocyclic Chemistry.

X-ray crystallographic analysis and the photochemical aspects of N,N-diallylcoumarincarboxamides were investigated. Irradiation of the corresponding amides promoted stereoselective intramolecular cyclobutane formation exclusively. The solid-state photoreaction of the coumarinamide without substituent on the 4-position proceeded in a crystal-to-crystal manner. On the other hand, photolysis of the amide possessing a methyl group at the 4-position also effected 2+2 cycloaddition; however, the reaction proceeded much slower. The difference in the reactivity was explainable on the basis of the molecular conformation in the crystal lattice. (c) 2006 Elsevier Ltd. All rights reserved.

Synthesis of optical active compounds from achiral or racemic materials is one of the most impressive studies in organic chemistry. Here we provide two new technique of generation of optical activity without anyl outside chiral source. One is the breaking of chiral symmetry of axially chiral materials via racemization-preferential crystallization method. Another involves the asymmetric reaction using the frozen chirality generated by chiral crystallization of achiral materials.

A series of chiral aminophosphine ligands with N, N-disubstituted 2-diphenylphosphinoaniline backbone are designed and readily prepared from (R)-2-(methoxymethyl)pyrrolidine or (S)-prolinol. The reactivity and selectivity in the palladium-catalyzed asymmetric allylic alkylation (AAA reaction) of 1,3-diphenyl-2-propenyl acetate with a dimethyl malonate-BSA-LiOAc system using these chiral ligands are evaluated. Furthermore, chiral fluorous aminophosphine bearing two fluo rous ponytails was prepared from (S)-prolinol. Chiral fluorous palladium catalyst from this ligand was easily reused in palladium-catalyzed AAA reaction with good enantipselectivity.

Quaternary chiral carbons were effectively generated from tertiary chiral carbons via photochemical intramolecular β-hydrogen abstraction reaction of thioimides involving the highly-controlled chiral-memory effect. © The Royal Society of Chemistry 2006.

Chiral fluorous aminophosphine 4c bearing two fluorous ponytails was prepared from (S)-prolinol and applied to palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate (7) with a dialkyl malonate-BSA-LiOAc system with high enantioselectivities (up to 97% ee). Results indicated that the chiral fluorous palladium catalyst from ligand 4c was easily separated from the reaction mixture by simple solid/liquid separation and could be reused up to five times. © 2005 American Chemical Society.

(Chemical Equation Presented) Frozen chirality: Achiral naphthamide 1 can be crystallized to give chiral 1*, whose chiral molecular conformation is retained ("frozen") after the crystals are dissolved in cold THF. Asymmetric photocycloaddition of 1* with 9-cyanoanthracene (9-CNAN) in solution gives cycloadduct 2 with high enantioselectivity. © 2005 Wiley-VCH Verlag GmbH &amp Co. KGaA.

Commercially available, inexpensive N-phenyldiethanolamine (6) is an efficient ligand for zinc-catalyzed transesterification. The use of 6/Et 2Zn for reactions between various alcohols and vinyl acetate at room temperature produced the desired products in good yields. © 2005 Elsevier Ltd. All rights reserved.

N,N-Diisopropylcarbamoylisatin showed polymorphism and was crystallized into two different space groups, chiral P2(1)2(1)2(1) and racemic P2(1)/c from the solvent; the polymorphism could be controlled by crystallization from the melt using the difference of melting points. (c) 2005 Elsevier Ltd. All rights reserved.

(Chemical Equation Presented) Glyoxal bis(N-methyl-N-phenylhydrazone) (1) and its related compounds such as 2-pyridinecarboxaldehyde N-methyl-N- phenylhydrazone (3) were prepared and examined as ligands for the Suzuki-Miyaura cross-coupling reaction of aryl halides and arylboronic acids. We found phosphine-free catalysts, such as Pd(OAc)2/hydrazone ligand 1 or 3, to be efficient catalysts for a variety of substrates to produce the coupling products in good yields. © 2005 American Chemical Society.

(Chemical Equation Presented) Chiral diaminophosphines 4 were prepared from (S)-prolinol-derived aminophosphine oxide 5 by bromination with ring expansion followed by animation with ring contraction and reduction, using trichlorosilane. In the presence of 4 as a ligand, palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate (11) with a dialkyl malonate-BSA-LiOAc system was successfully carried out with good enantioselectivities (up to 98% ee). © 2005 American Chemical Society.

The photochemical reactions of 2-acylphenyl methacrylates (=2-acylphenyl 2-methylprop-2-enoates) 1 were investigated. Irradiation of 2-acylphenyl methacrylates 1a-d in MeCN gave the tricyclic lactones 2a-d in good yields, together with a small amount of O-C=O bond cleavage product, the 2-acylphenols 3a-d (Scheme 2, Table). The formation of the tricyclic lactones 2 probably follows a mechanism involving a 1,7-diradical through ζ-H abstraction (1,8-H transfer) by the excited carbonyl O-atom (Scheme 3). Irradiation of 2-acylphenyl tiglate (=2-acylphenyl (2E)-2-methylbut-2-enoate) 1e and 2-acylphenyl methacrylates 1g-i, substituted by a MeO group (δ-H) at the 3,5-positions of the phenylgroup, also gave the tricyclic lactones 2e and 2g-i, but in low yields. On the other hand, no H-abstraction products were observed on irridation of 2-(ethoxycarbonyl)phenyl methacrylate 1f, of 2-acylphenyl methacrylate 1j which is substituted by a Me group (γ-H) at the 3,5-positions of the phenyl group, and of 1k with an OH group at the 3-position of the phenyl group. © 2005 Verlag Helvetica Chimica Acta AG.

The photochemical reactions of different N-(2-acylphenyl)-2-bromo-2- methylpropanamides have been investigated. Irradiation of the N-unsubstituted anilides 1a-1c gave the corresponding dehydrobromination, cyclization, and bromo-migration products 2, 3, and 4, respectively (Table 1). Irradiation of the N-alkyl anilides 1e-1g afforded the corresponding deacylation and cyclization products 5 and 6, respectively, whereas irradiation of the N-alkyl anilides 1i-1k, carrying 2-benzoyl groups on the aromatic rings, afforded the unexpected tricyclic lactams 7 (besides 2, 5, and 6). The formation of the cyclization products 6 could be rationalized in terms of an electrocyclic ring closure of the 6π-electron-conjugated enamides 2 produced by dehydrobromination of 1, followed by thermal 1,5-acyl migration (Path B in the Scheme). The formation of the bridged lactams 7 probably follows a mechanism involving the 1,7-diradical 8 generated by ζ-H-abstraction (1.8-H transfer) by an excited acyl O-atom (Path A). © 2005 Verlag Helvetica Chimica Acta AG.

The photochemical reactions of various 'N-methacryloyl acylanilides' (= N-(acylphenyl)-2-methylprop-2-enamides) have been investigated. Under irradiation, the acyl-substituted anilides 1a-1c and 1o afforded exclusively the corresponding quinoline-based cyclization products of type 2 (Table 1). In contrast, irradiation of the benzoyl (Bz)-substituted anilides 1e-1h afforded a mixture of the open-chain amides 4e-4h and the cyclization products 2e-2h. Irradiation of the para-acyl-substituted anilides 6a-6e and 6h afforded the corresponding quinoline-based cyclization products of type 5 as the sole products (Table 2). The formation of the cyclization products 2a-2c and 2o can be rationalized in terms of 6π-electron cyclization, followed by thermal [1,5] acyl migration, and that of compounds 3p, 5a-5e, and 5h can be explained by a 6π-electron cyclization only. The formation of the open-chain amides 4e-4h probably follows a mechanism involving a 1,7-diradical, C and a spirolactam of type D (Scheme). Long-range ζ-H abstraction by the excited carbonyl O-atom of the benzoyl group on the aniline ring is expected to proceed via a nine-membered cyclic transition state, as proposed on the basis of X-ray crystallographic: analyses (Fig. 2). © 2005 Verlag Helvetica Chimica Acta AG, Zürich.

A series of optically active 1,4-aminoalcohols were synthesized from the corresponding lactones, which were prepared from (+)-camphor and (—)-fenchone, via hydroxy amides. The addition reactions of diethylzinc to aldehydes using the 1,4-aminoalcohols as chiral catalysts were investigated. 1,4-Aminoalcohol catalysts derived from (+)-camphor resulted in secondary (S)-alcohols as the major product. The 1,4-aminoalcohols bearing two propyl groups achieved the highest enantioselectivity the enantiomeric excess was 95%. 1,4-Aminoalcohol catalysts derived from (—)-fencone resulted in secondary (R)-alcohols as the major product. In the chiral 1,4-aminoalcohols from (—)-fencone, the alcohol containing a morpholine structure appended to the amino group possessed the highest enantioselectivity with an enantiomeric excess of 79%. © 2005, Japan Oil Chemists' Society. All rights reserved.

A series of novel chiral aminophosphine ligands are designed and readily prepared from (S)-prolinol. The reactivity and selectivity in the palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with a dimethyl malonate-BSA-LiOAc system using these chiral ligands are evaluated, and the structural elucidation of ligands and palladium complex is also conducted. Moreover, a series of trialkylsilylated chiral aminophosphine ligands are prepared and applied to palladium-catalyzed asymmetric allylic alkylation (up to 98% ee).

Irradiation of a benzene solution of 2-alkoxy-3-cyanopyridines in the presence of 2-cyanofuran gave 4+4 photoadducts in good yields, and the structure was established by X-ray single crystal analysis. (C) 2004 Published by Elsevier Ltd.

2-(1-indolinyl)benzaldehyde dimethylhydrazones are prepared by nucleophilic aromatic substitution of the corresponding 2-fluorobenzaldehyde dimethylhydrazones with lithiated indoline in good yields.

Reaction of the chiral crystals of the achiral amides with n-butyllithium in toluene at −80 °C gave optically active alcohols in 17–84% ee. © 2014 The Royal Society of Chemistry.

The existence of 3 as a pair of stable atropisomers has been demonstrated analytically through chiral phase LC-CD investigations. Resolution of 3d was achieved by preparative chiral HPLC. Finally, the ability of the first C(aryl)-N(amine) axially chiral phosphine ligand 3d is demonstrated in a catalytic asymmetric reaction. © 2003 Elsevier Ltd. All rights reserved.

New type chiral ligands 3, which have a chiral carbon center and stable C(aryl)-N(amine) axial chirality, were prepared from chiral prolinol-derived aminophosphine oxide 4. Pd-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate (6) with a dimethyl malonate-BSA-LiOAc system was successfully carried out in the presence of 3d resulting in a good yield with good enantioselectivity (up to 95% ee). © 2003 Elsevier Science Ltd. All rights reserved.

Glyoxal bis(methylphenylhydrazone) 1 was prepared and examined as a ligand for the Suzuki-Miyaura cross-coupling reaction of aryl bromides and arylboronic acids. We found phosphine-free catalyst, such as Pd(OAc)2/hydrazone ligand 1 to be an efficient catalyst for a variety of substrates to produce the coupling products in good yields at room temperature.

Chiral hydrazone ligands 2 are easily accessible in good yields by nucleophilic phosphanylation of corresponding orthofluorobenzaldehyde SAMP hydrazone derivatives with KPPh2. Palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate (6) with a dimethyl malonate-BSA-LiOAc system has been successfully carried out in the presence of chiral hydrazone ligands 2g in high yields with high enantioselectivities. © 2002 Elsevier Science B.V. All rights reserved.

Asymmetric synthesis using frozen chirality generated by spontaneous crystallization was performed. Achiral asymmetrically substituted imide with a tetrahydronaphthyl group on the nitrogen atom crystallized in a chiral fashion, with space group P212121. The molecular chirality generated by spontaneous crystallization was retained in cold THF. The half-life determined on the basis of decreasing optical activity followed by CD spectrometer was 7.8, 33.1, and 150.0 min at -20, -30, -40 °C, respectively. The energy barrier (ΔG‡) of racemization was calculated with the temperature dependence of the kinetic constant to be 18.24-18.36 kcal mol-1 at 233-253 K. The memorized frozen chirality was transferred to permanent optically active alcohols by nucleophilic addition with n-buthyllithium.

Irradiation of a benzene solution of 3-cyano-2,6-dimethoxypyridine in the presence of ethyl vinyl ether (EVE) gave 1:1 photoadducts, 3-cyano-5-ethoxy-2,8-dimethoxy-4,5-dihydroazocine, in good yields, whose structure was established by X-ray single-crystal analysis. The photoadduct was produced via cycloaddition between the C3-C4 position of the pyridine derivatives and an alkene chromophore. On the other hand, 3-cyano-2,6-dimethoxy-4-methylpyridine cycloadds to EVE at the C2-C3 position of the pyridine ring upon irradiation. The difference is explained on the basis of the steric effect.