HETEROCYCLES

■ Contents

■ Pyrrolotetrazoles and Ring-Fused Derivatives

Dietrich Moderhack*

*Institute of Medicinal and Pharmaceutical Chemistry, Technical University, Braunschweig, Beethovenstrasse 55, D-38106, Germany

Abstract

The preparative chemistry of seven types of pyrrolotetrazoles (formally: pyrrolo[1,2-d]tetrazoles) A–G including five ring-fused derivatives such as B', B'', C', C'', and E' is surveyed in this article. Theoretical work on annular tautomerism and pyrrolotetrazole–azidopyrrole isomerism is dealt with complementarily.

■ 9,9'-Bi(xanthene)-Type Hexaphenylethane Derivatives as Advanced Organic Electrochromic Systems

Takanori Suzuki,* Yusuke Ishigaki, Masaki Takata, Jun-ichi Nishida, and Takanori Fukushima

*Department of Chemistry, Faculty of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan

Abstract

9-Phenylxanthenyl radical can undergo facile C-C bond formation at C9-position when the two units of the radical are connected at C2'-positions to give stable intramolecular dimer (1), which is a clamped hexaphenylethane derivative with an elongated C-C bond. The newly formed bond in 1 can be cleaved easily upon two-electron oxidation to give bis(9-xanthenylium)-type dication (22+), from which the diradical is generated upon two-electron reduction. This review account describes the dynamic redox ("dyrex") pair of colorless 1 and yellow-orange 22+, which provides a versatile scaffold to develop multi-functional electrochromic systems. Both of 1 and 22+ are sterically challenged molecules and thus adopt characteristic skewed geometries. Electrochiroptical response was realized by suppressing the chiral inversion of helicity in 1 and axial chirality in 22+ whereas redox-induced fluorescence switching was attained by attaching the fluorophore whose emission is quenched by xanthenylium in 22+ but not by spiro(xanthene) unit in 1. By the molecular design that allows intramolecular chiral transmission, the spectral changes were also induced by the external stimuli (e.g. heat, pH) other than redox input, which made it possible to construct less well-explored multi-input-multi-output response systems. More advanced functions could be endowed, such as chiral redox memory or reversible O2-storage, by further modification of the prototype.

■ The Electronic Structure of Thioxanthylium Scaffolds

Koki Hirano, Akira Yasuda, Takahiro Sasamori, Kosei Shioji, Kentaro Okuma, and Noriyoshi Nagahora*

*Department of Chemistry, Faculty of Science, Fukuoka University, Nanakuma 8-19-1, Jonan-ku, Fukuoka, Fukuoka 814-0180, Japan

Abstract

A new series of thioxanthylium trifluoromethanesulfonates has been synthesized via a trifluoromethanesulfonic-acid-induced cyclization of thioether precursors. The electronic structure of these thioxanthylium salts were determined by UV−vis absorption spectroscopy, and theoretically investigated by density functional theory calculations.

■ Efficient Approach towards the Polysubstituted 4H-Pyran Hybrid Quinolone Derivatives and Subsequent Copper-Catalyzed Hydroxylation of Haloarenes

Vipin Kumar, Dharmender Singh, Raghuram Gujjarappa, Chandi C. Malakar,* and Virender Singh*

*Department of Chemistry, National Institute of Technology Manipur, Langol, Imphal-795004, Manipur, India

Abstract

A proficient and feasible approach towards polysubstituted quinolone conjugated 4H-pyrans has been elucidated. The illustrated phenomenon concern with the base-mediated multicomponent reaction and subsequent copper-catalyzed hydroxylation of C-X bond emerging in an amide functionality. The developed reaction conditions showcased considerable substrate scope and functional group tolerance by giving the desired products in good yields.

■ DBU-Catalyzed Highly Efficient Synthesis of 1,4-Dihydropyridine Derivatives from Arylidenemalononitriles and β-Enamino Imides

Wei Han, Kazuya Nakajima, Masashi Kajitani, and Takeshi Oriyama*

*Department of Chemistry, Faculty of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan

Abstract

Various 1,4-dihydropyridine derivatives were efficiently synthesized from arylidenemalononitriles and β-enamino imides using DBU (3 mol%) as the catalyst at room temperature. This mild, straightforward high-yielding protocol was atom-economy, time-economy, with a low catalyst load, and without the need for reflux.

■ Construction and Biological Evaluations of Some Novel Chromeno[2,3-b]pyridines and Chromeno[2,3-b]quinolines Using 6-Methylchromone-3-carbonitrile

Magdy A. Ibrahim* and Nasser M. El-Gohary

*Department of Chemistry, Faculty of Education, Ain Shams University, Cairo, Egypt

Abstract

Reaction of 6-methylchromone-3-carbonitrile (1) with acetylacetone under basic conditions afforded 3-acetyl-2,7-dimethyl-5H-chromeno[2,3-b]pyridin-5-one (2) which utilized as a starting substrate. Condensation of compound 2 with a variety of amines and hydrazines produced chromeno[2,3-b]pyridines linked variable compounds in the same molecular frame. Condensation reaction of compound 2 with variable carbon nucleophilic reagents namely; malononitrile, ethyl cyanoacetate, malononitrile dimer, 1H-benzimidazol-2-ylacetonitrile and dimedone produced heteroannulated chromeno[2,3-b]quinolines 18-22. The synthesized compounds were screened in vitro for their antimicrobial activity and revealed remarkable inhibitory effects against the selected microorganisms. Structures of the newly synthesized products have been deduced upon the help of elemental analysis and spectral data (IR, 1H NMR, 13C NMR and mass spectra).

■ Synthesis and in vitro Biological Evaluation of Cananodine

Abdullah Yusuf,* Paruke Aibibula, Ju-Bao Zhang, Guo-Zheng Huang, Haji Akber Aisa, and Jiang-Yu Zhao*

*College of Chemistry and Environmental Science, Laboratory of Xinjiang Native Medicinal and Edible Plant Resources Chemistry, Kashgar University, Xueyuan Road 29, Kashgar 844000, P. R. China

Abstract

(±)-Cananodine was obtained by common reactions from (±)-rupestine G and was isolated and synthesized by our group. (+)-Cananodine and its enantiomer were obtained by chiral separation and their absolute configurations were determined by high-resolution mass spectrometry, nuclear magnetic resonance, and electronic circular dichroism spectroscopy. The optical rotation of both cananodine and its enantiomer were re-treated. Biological activity against Hep G2, Hela, and MDA-MB-231 were also investigated.

■ Acetate/Acetic Acid-Assisted One-Pot Synthesis of (Diarylmethylene)imidazolone from Amide or Thioamide

Masahiro Ikejiri,* Atsufumi Watanabe, Mari Katsuda, Mayu Funakoshi, Aki Fujisaka, and Kazuyuki Miyashita*

*Faculty of Pharmacy, Osaka Ohtani University, Nishikiori-Kita 3-11-1, Tondabayashi, Osaka 584-8540, Japan

Abstract

With the aim of extending the library of green fluorescent protein chromophore analogs, a facile one-pot synthesis of 5-(diarylmethylene)imidazolones from the corresponding amide or thioamide is described. Isolation of unstable imidate intermediates is not required, thereby circumventing the drawback of previous approaches. A reaction mechanism in which both acetate and acetic acid promote the imidazolone formation is proposed.

■ Efficient Synthesis of Acrylates Bearing an Aryl or Heteroaryl Moiety: One-Pot Method from Aromatics and Heteroaromatics Using Formylation and the Horner-Wadsworth-Emmons Reaction

Tatsuro Yasukata* and Takaharu Matsuura

*API R&D Laboratory, CMC R&D Division, Shionogi & Co., Ltd., 1-3 Kuise Terajima 2-chome, Amagasaki, Hyogo 660-0813, Japan

Abstract

Acrylates bearing an aryl or heteroaryl moiety were efficiently prepared by a one-pot process employing a sequence of lithiation, formylation and the Horner-Wadsworth-Emmons reaction starting from aromatic and heteroaromatic compounds. This method can efficiently introduce an acrylate moiety into aromatic and heteroaromatic compounds.

■ Stepwise Reactions between Cyclic 1,4-Diazadienes and Ketenes: Characteristics and Mechanism

Kazuhide Nakahara,* Koki Yamaguchi, and Hisao Kansui

*Department of Integrative Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan

Abstract

The reaction of unsymmetrical monophenyl cyclic 1,4-diazadienes with ketene derivatives yields new structures via 1,5-sigmatropic reactions. These structures were determined and confirmed by single-crystal X-ray analysis. The reaction mechanism was investigated by density functional theory calculations. The result of the calculation indicated whether the reaction was a cyclization reaction or a 1,5-shift rearrangement based on the stability of the intermediate conformation.