Isao Azumaya

Stereochemistry of N-methylbenzanilide and benzanilide

Abstract The structure of N-methylbenzanilide was elucidated by X-ray analysis and examination of 1 H- and 13 C-nmr spectra. The stereochemistry of the amide bond was proved to be cis in the crystal and in solution, whereas that of benzanilide is trans .

Stereochemistries of aromatic N-methylamides in crystal and solution. Temperature-dependent conformational conversion and attracting aromatic-aromatic interactions

Abstract Crystal structures and dynamic behavior in solution of some aromatic N-methylanilides were analyzed. Every N-methylamide examined was in cis form in the crystal, and exhibited cis-preference in solution. Among them, meta-substituted amides, such as N,N′,N″-trimethyl-N,N′,N″-triphenyl-1,3,5-benzenetricarboxamide (5), exist in the all-syn conformation, in which all the N-phenyl groups are on the same side of the plane of the central benzene ring in the crystal. 1H-NMR studies suggested that 5 existed mainly in all-syn conformation at low temperature as found in the crystal, while the anti conformation, in which one N-phenyl group is on the opposite side of the central benzene ring, becomes predominant at higher temperature, and a rapid equilibrium exists between the syn and the anti conformations. This is a result of the positive enthalpy (ΔH0 = + 2.1 kcal/mol) and the identical-signed large entropy (ΔS0 = + 8.4 cal/mol·K) for the conversion from syn to anti conformation. From NMR experiments, the enthalpy gained by assembly of the three phenyl groups in solution was deduced to be 2.8 kcal/mol.

FACILE FORMATION OF AROMATIC CYCLIC N-METHYLAMIDES BASED ON CIS CONFORMATIONAL PREFERENCE

Abstract Treatment of meta -(methylamino)benzoic acid ( 2 ) with tetrachlorosilane afforded several cyclic oligomers ( 3 – 6 ). All the amide bonds of the four oligomers are cis in the crystal. 1 H-NMR spectra of the trimer 3 showed the existence of an equilibrium between chiral truncated cone ( syn ) and anti conformations.

Helical aromatic urea and guanidine

N , N ′-Dimethyl- N , N ′-dipheylurea ( 1 ) and N , N ′-Dimethyl- N , N ′-diphenyl-guanidinium bromide ( 2 ) each have folded structures with the two phenyl groups located face-to-face. Oligomeric compounds 3 and 4 , having five benzene rings connected at the meta positions by cis -urea or guanidino groups, form aromatic layered helices in the crystal state. The crystals are racemic with a 1:1 enantiomer ratio. They exhibit stacked ( 3 ) or zigzag chain ( 4 ) packing, reflecting displaced parallel structure for the terminal phenyl groups of neighboring molecules of 3 and tilted T-shaped structure for those of 4 , respectively.

Au(III)/TPPMS-catalyzed benzylation of indoles with benzylic alcohols in water.

A novel and efficient method for the Au(III)/TPPMS-catalyzed direct substitution reaction of benzhydryl and benzylic alcohols with indoles in water is developed. Au(III)/TPPMS is an effective catalyst for the benzylation of the strong π nucleophile 1-methylindole, while common Brønsted or Lewis acids are ineffective.

A chiral N-methylbenzamide: Spontaneous generation of optical activity

Abstract 1,2-Bis(N-benzoyl-N-methylamino)benzene (1) was crystallized from distilled ethyl acetate as chiral crystals belonging to space group P212121. The optically active crystals of the two enantiomers were distinguishable morphologically, and their CD spectra in KBr were mirror images. In solution, several conformational isomers due to rotations of the ArN bonds and the amide bonds were observed. The major conformer corresponds to the crystal structure in which the two N-benzoyl groups exist on opposite sides of the central benzene ring (anti conformation) and the amide bonds are both cis. The enantiomers in solution could be distinguished from each other by 1H-NMR measurements in the presence of chiral 1,1′-bi-2-naphthol. Mixed crystals of 1 and (R)-1,1′-bi-2-naphthol were obtained from their 1:1 mixed solution in MeOH. An X-ray crystallographical analysis showed that the configuration of 1 in the mixed crystals was (R,R). 1H-NMR measurements of the mixed crystals at 178 K in CD2Cl2 showed the absolute configuration of 1 in the CD260-(+)-crystal to be (R,R).

Chemoselective Benzylation of Unprotected Anthranilic Acids with Benzhydryl Alcohols by Water-Soluble Au(III)/TPPMS in Water

A novel and efficient method for the benzylation of unprotected anthranilic acids with benzhydryl alcohols using water-soluble Au(III)/TPPMS in water is developed. Water plays an important role in our catalytic system. This new protocol could be used for not only N-benzylation, but also chemoselective C-benzylation by the Friedel-Crafts reaction.

Helicity Induction in Three π‐Conjugated Chromophores by Planar Chirality of Calixamide

Shall we twist? Three-dimensional arrangement of π-conjugated chromophores with triple-stranded helicity was achieved by using the planar chirality of m-calix[3]amide. Based on spectroscopic data and theoretical calculations, the dynamic and preferred helical characters of bithiophene units embedded in the tubular molecule were elucidated, and the absolute configuration was determined.

Benzoyl methyl phosphates as efficient reagents in the one-pot tandem approach for the synthesis of 2-phenylbenzimidazoles in water

A novel and efficient method for the environmentally benign, catalyst- and auxiliary-free synthesis of 2-phenylbenzimidazoles in water is developed. Benzoyl methyl phosphates play important roles as biomimetic acylating agents for the one-pot tandem approach without additional catalysts.

A layered artificial dinucleotide complex

An X-ray diffraction analysis of the 1:1 complex ofN, N′-dimethyl-N, N′-bis[2-(3-methylureido)pyrid-5-yl]urea (1) and a 1, 3-bis(cytosyl)propane derivative (2a) revealed layered triply-hydrogen-bonded pairings. The conformation of1 in the complex is similar to that in the crystal structure of1 alone, withanti conformation of the two aromatic rings. A unique heterodimer formation with aromatic layered structure is formed between artificial nucleotide analogs1 and2a, based on thecis conformational preference of1. Figure options Download full-size image Download as PowerPoint slide