坂本 昌巳

© 2018 the Partner Organisations. Regrettably, in the original article on page 981 the wrong name was provided for compound 4b. The correct name of compound 4b is 1-cinnamyl-2-phenylnaphtho[2,1-b]furan. Moreover, some of the structures described in Table 2 are incorrect. The correct structures are shown below. (Table Presented).

We previously reported the synthesis of BICMAP (1a) via 6-diphenylphosphino-2,3-dihydrobenzofuran as a key intermediate. However, we did not successfully synthesize BICMAP analogues via a similar synthetic route. Herein we report the second-generation synthesis of BICMAP and its derivatives via diethylphosphonate as a key intermediate.

We found that the hydrazone-Pd-catalyzed direct intermolecular reaction of o-alkynylphenols with allylic acetates afforded the corresponding 2-substituted-3-allylbenzofuran derivatives. This reaction proceeded smoothly at room temperature using a hydrazone-Pd catalyst system.

C2-Symmetric cyclic polyethers were conveniently provided by the photochemical dimerization of covalently-linked 2-chromonecarboxylic esters. Irradiation of polyethers possessing 2-chromonecarboxylate groups at both ends efficiently promoted intramolecular [2+2] cyclobutane formation leading to 14- to 23-membered cyclic polyethers in good chemical yields and quantum efficiencies. X-ray crystallographic analysis revealed that the stereochemistry of the cyclobutane was the C2-symmetric structure.

Asymmetric synthesis involving photochemical dimerization of a prochiral flavonoid derivative in solution without any chiral source was achieved. Irradiation of ethyl 6-bromochromonecarboxylate in solution efficiently gave a C2-chiral anti-head-to-head dimer in excellent chemical yield with good quantum efficiency (Φ365 = 0.15). X-ray crystallographic analysis revealed that the dimer crystallized as a conglomerate of C2 space group. The crystalline dimer precipitated upon irradiation of the monomer in solution, and indirect racemization of the dimer through a reversible photoreaction in solution and selective crystallization simultaneously occurred to give the C2-chiral dimer in optically active form with up to 80 % ee. Optically active photoproducts could be obtained by simply irradiating achiral materials in solution without an external chiral source.

Asymmetric synthesis involving photochemical dimerization of a prochiral flavonoid derivative in solution without any chiral source was achieved. Irradiation of ethyl 6-bromochromonecarboxylate in solution efficiently gave a C-2-chiral anti-head-to-head dimer in excellent chemical yield with good quantum efficiency (phi(365) = 0.15). X-ray crystallographic analysis revealed that the dimer crystallized as a conglomerate of C2 space group. The crystalline dimer precipitated upon irradiation of the monomer in solution, and indirect racemization of the dimer through a reversible photoreaction in solution and selective crystallization simultaneously occurred to give the C-2-chiral dimer in optically active form with up to 80%ee. Optically active photoproducts could be obtained by simply irradiating achiral materials in solution without an external chiral source.

We designed and synthesized dimeric imidazo[1, 5-a]pyridines possessing various aryl groups at 1,1'-positions. The solution of these derivatives exhibited fluorescence emission in wavelength range of 487-512 nm. The fluorescence emissions were slightly red-shifted under acidic condition by addition of trifluoroacetic acid. Furthermore, the original fluorescence spectra were observed after the addition of triethylamine as a base.

Irradiation of prochiral (E)-aroylacrylamide with sunlight gave single-handed pyrrolinone quantitatively and with an enantiomeric excess (ee) of over 99 % under absolutely achiral conditions. The phenomenon was explained by photoisomerization and reversible cyclization followed by dynamic crystallization involving deracemization.

Irradiation of prochiral (E)-aroylacrylamide with sunlight gave single-handed pyrrolinone quantitatively and with an enantiomeric excess (ee) of over 99% under absolutely achiral conditions. The phenomenon was explained by photoisomerization and reversible cyclization followed by dynamic crystallization involving deracemization.

2-Propoxy-1-naphthamide possessing a chiral 2-methylpyrrolidine group exists as a mixture of four diastereomers owing to the rotation of the Ar-(C=O) and C-center dot(=O)-N bonds. The diastereomers existed in the ratio of 32:32:14:22 in CD3OD. When the MeOH solution of the mixture of diastereomers was irradiated with Pyrex filtered UV light (>290 nm) from a high-pressure mercury lamp, the ratio changed to 27:4:43:26. The diastereomeric ratio was reversibly controlled by irradiation and heat. The change was accurately reflected in the intensity of the CD spectra. Furthermore, the reversible axial chirality was transferred to the optical activity of asymmetric reaction products via the photochemical cycloaddition reaction with 9-cyanoanthracene. (C) 2015 Elsevier B.V. All rights reserved.

Unprecedented absolute asymmetric synthesis was carried out using frozen chirality derived from chiral crystals of achiral coumarin-3-carboxamide and carbenoids. An enantioselective cycloaddition reaction with a sulfur ylide gave an optically active cyclopropane up to 97% ee. Furthermore, a cycloaddition reaction with dichlorocarbene gave dihydrofuran in 93% ee. Nucleophilic addition of ylide or carbene occurs from the side of the carbonyl oxygen atom to avoid steric hindrance of substituents on the nitrogen atom.

Single-handed -amino acid derivatives were generated from achiral precursors without an external chiral source. Conjugate addition of phenethylamine to an achiral aroyl acrylamide under homogeneous conditions gave the -amino amides in quantitative yields, which crystallized as a conglomerate of a P2(1) crystal system. Dynamic preferential crystallization or attrition-enhanced deracemization resulted in the formation of enantiomorphic crystals of 99% ee.

Unprecedented absolute asymmetric synthesis was carried out using frozen chirality derived from chiral crystals of achiral coumarin-3-carboxamide and carbenoids. An enantioselective cycloaddition reaction with a sulfur ylide gave an optically active cyclopropane up to 97% ee. Furthermore, a cycloaddition reaction with dichlorocarbene gave dihydrofuran in 93% ee. Nucleophilic addition of ylide or carbene occurs from the side of the carbonyl oxygen atom to avoid steric hindrance of substituents on the nitrogen atom.

Single-handed α-amino acid derivatives were generated from achiral precursors without an external chiral source. Conjugate addition of phenethylamine to an achiral aroyl acrylamide under homogeneous conditions gave the α-amino amides in quantitative yields, which crystallized as a conglomerate of a P21crystal system. Dynamic preferential crystallization or attrition-enhanced deracemization resulted in the formation of enantiomorphic crystals of 99 % ee.

A new class of C-2 chiral materials was easily prepared by the photodimerization reaction of (R)-N-phenethy1-2-chromonecarboxamide followed by recrystallization. Reduction of the photodimer gave the corresponding alcohol stereoselectively. Both C-2 chiral materials worked effectively as ligands for enantioselective ethylation of arylaldehydes using diethylzinc. (C) 2015 Elsevier Ltd. All rights reserved.

Crystallization-induced asymmetric transformation (CIAT) of axially chiral materials is summarized on the basis of our studies. CIAT can be classified into two categories, Crystallization-Induced Enantiomer Transformation (CIET) and Crystallization-Induced Diastereomer Transformation (CIDT). Racemic mixtures or diastereomixtures that exist as a mixture of stereoisomers in solution converge on a single stereoisomer by dynamic crystallization. Many axially chiral materials, such as N-arylpyrimidine-2-(1H)-ones and -thiones, were crystallized as conglomerates, and total resolution was performed with high enantiomeric purities from the solution by CIET. Dynamic resolution of aromatic amides, such as 2-alkoxy-1-naphthamides, 2-quinolone-3-carboxamide, coumarin-3-carboxamide, and nicotinamides, was also successfully achieved by crystallization from the melt with high ees. Furthermore, optically active materials tend to crystallize in a chiral fashion, and CIDT is useful to obtain single diastereomers from a mixture of many diastereomers. Many types of aromatic amides with chiral auxiliaries were crystallized in a chiral fashion and were easily resolved by dynamic crystallization from the melt. Salt formation of oily racemic nicotinamides with enantiopure acid involving racemization during salt formation also gave diastereopure salts. The optical activity of the materials resolved by dynamic crystallization was effectively transferred to the products by many kinds of asymmetric reactions.

シンナミル構造またはプレニル構造を有する新規エーテル類を合成し、これらの香気について検討した。また、これらの最安定化構造をGaussian 09プログラムによる量子化学計算にて求め、立体構造が香気に与える影響についてさらに検討した。

We report a new catalyst system, morpholine-NiCl2, for the Suzuki-Miyaura coupling of aryl chlorides with aryl-or alkenylboronic acids to give biaryl compounds. This catalyst system is easy to apply on a large scale because of its easy preparation and the use of inexpensive reagents. In addition, analysis of the residual nickel shows only 9.7 ppm remaining after normal work-up. This catalyst system has been applied to 26 compounds to give a variety of biaryl products, including hetero-biaryl compounds.

An asymmetric photoreaction by using chirality provided by dynamic chiral salt formation was demonstrated. Crystallization of racemic 2-quinolone-3-carboxamide and 2-quinolone-4-carboxamide with enantiopure L-dibenzoyltartaric acid led to deracemization and gave high diastereomeric excess values of the crystalline salts in almost quantitative yield. The axial chirality was retained for a long period of time after the salts were dissolved in cooled solvent. The frozen chirality derived from the chiral salts was effectively transferred to the products by using a typical [2+2] photocycloaddition reaction with alkenes. Crystallization of racemic quinolonecarboxamides with enantiopure L-dibenzoyltartaric acid (L-DBTA) leads to deracemization. The axial chirality is retained for a long period of time after the salts are dissolved in cooled solvents, and this frozen chirality can be effectively transferred to the products by using a typical [2+2] photocycloaddition reaction with alkenes CIDT = crystallization-induced diastereomer transformation.

An asymmetric photoreaction by using chirality provided by dynamic chiral salt formation was demonstrated. Crystallization of racemic 2-quinolone-3-carboxamide and 2-quinolone-4-carboxamide with enantiopure L-dibenzoyltartaric acid led to deracemization and gave high diastereomeric excess values of the crystalline salts in almost quantitative yield. The axial chirality was retained for a long period of time after the salts were dissolved in cooled solvent. The frozen chirality derived from the chiral salts was effectively transferred to the products by using a typical [2+2] photocycloaddition reaction with alkenes.