HETEROCYCLES

■ Contents

■ Heterocyclization with Some Heterocyclic Diamines: Synthetic Approaches for Nitrogen Bridgehead Heterocyclic Systems

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

*Department of Chemistry, Faculty of Education, Ain Shams University, Roxy, Cairo 11711, Egypt

Abstract

This review represents the methods developed for the synthesis of a variety of nitrogen bridgehead heterocyclic systems such as [1,2,4]triazolo[1,5-a]pyridines, pyrido[1,2-b][1,2,4]triazines, pyrido[1,2-b][1,2,4]triazepines, pyrazolo [1,5-b][1,2,4]triazole, pyrazolo[1,5-b][1,2,4]triazine, pyrazolo[1,5-b][1,2,4]triazepine, [1,2,4]triazolo[3,4-b][1,2,4]triazine, [1,2,4]triazolo[4,3-b][1,2,4]triazepines, pyrimido[3,4-b][1,2,4]triazine from the heterocyclization of some heterocyclic diamines with a variety of electrophilic reagents.

■ C-H Trifluoromethylations of 1,3-Dimethyluracil and Reactivity of the Products in C-H Arylations

Miroslava Ćerňová, Radek Pohl, Blanka Klepetářová, and Michal Hocek*

*Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nam. 2, CZ-16610 Prague 6, Czech Republic

Abstract

Diverse electrophilic, nucleophilic and radical C-H trifluoromethylations of 1,3-dimethyluracil were systematically studied in order to prepare either 5- or 6-(trifluoromethyl)uracil derivatives. Electrophilic reagents led only to dimeric bis-uracil products, whereas the radical trifluoromethylation by CF3SO2Na in presence of t-BuOOH gave 1,3-dimethyl-5-(trifluoromethyl)uracil (2) in good yield. The 6-(trifluoromethyl)uracil derivative 3 was only prepared in low yield and in a mixture with 2 by Ir-catalyzed borylation followed by treatment with the Togni's reagent. Attempted Pd-catalyzed C-H arylations of 2 in the presence of Cs2CO3 gave mixtures of de-trifluoromethylated products, whereas the reaction with 4-iodotoluene in the presence of CsF gave the desired 6-aryl-5-trifluoromethyluracil derivative 8 in moderate yield and the reaction was not general for other aryl halides.

■ Synthesis and Photophysical Properties of Diketopyrrolopyrrole-Based Near-Infrared Dyes

Takuya Yamagata, Junpei Kuwabara, and Takaki Kanbara*

*Graduate School of Pure and Applied Sciences, Tsukuba Research Center for Interdisciplinary Materials Science, University of Tsukuba, 1-1-1 Ten-nodai, Tsukuba-shi, Ibaraki 305-8573, Japan

Abstract

The introduction of phenylethynyl groups to boron-coordinated diketopyrrolopyrrole (DPP) derivatives resulted in the extension of π-conjugation, thereby showing bathochromic shifts of both absorption and emission wavelengths. The emission maximum of the DPP derivatives shifted to a near-infrared region.

■ Ring Transformation of the S-(2-Oxo-2,3-dihydro-1-benzofuran-3-yl)isothiuronium Bromides to 5-(2-Hydroxyphenyl)-2-imino-1,3-thiazolidin-4-ones

Richard Kammel and Jiří Hanusek*

*Institute of Organic Chemistry and Technology, University of Pardubice, Studentská 573, Pardubice, 532 10, Czech Republic

Abstract

Synthesis of thirteen substituted 5-(2-hydroxyethyl)-2-phenylimino-1,3-thiazolidin-4-ones is described starting from easily available and stable S-(2-oxo-2,3-dihydro-1-benzofuran-3-yl)isothiuronium bromides. The transformation proceeds under mild conditions, is very simple to perform, and is applicable to a wide range of substituents on isothiuronium moiety. Some 1,3-thiazolidin-4-ones show dynamic NMR behavior in solution because of prototropy tautomerism and E-/Z-stereoisomerism. Thermochromic behavior was observed for all synthesized compound.

■ Synethesis and Characterization of Di- and Tetrasubstituted p-tert-Butylthiacalix[4]arenes Containing Isatin Moiety at the Lower Rim

Siham Abd elrahman Lahsasni and Omran Abdellah Omran*

*Chemistry Department, Faculty of Science, Sohag University , Sohag 82524, Egypt

Abstract

Di- and tetrasubstituted p-tert-butylthiacalix[4]arene in three different conformers (cone, partial cone and 1,3-alternate) at lower rim, have been synthesized by the reaction of p-tert-butylthiacalix[4]arene and disubstituted p-tert-butylthiacalix[4]arene with isatin-3-[N2-(chloroacetyl)]hydrazone in acetone or acetonitrile in the presence of different alkali metal carbonates or hydroxide. Structures of the new compounds were established by elemental analyses and spectral data IR, 1H NMR, 13C NMR.

■ New Synthesis of N-(4-Chloro-3-cyano-7-ethoxyquinolin-6-yl)acetamide

Yongjun Mao, Yang He, Fuqiang Zhu, Weiming Chen, Jingshan Shen, and Jianfeng Li*

*Department of Medicinal Chemistry, Shanghai Institute of Materia Medica, 501 Haike Rd, Shanghai 201203, China

Abstract

New synthetic route of N-(4-chloro-3-cyano-7-ethoxyquinolin-6-yl)acetamide (1) is described on a hectogram scale. The key steps include the intramolecular cyclization of 3-amino-2-(2-chlorobenzoyl)acrylonitrile 22 to give the 3-cyano-4-quinolone 7, which was chlorinated by POCl3 to give the final product 1 in 36.9% yield over 9 steps and 98.9% purity (HPLC). Purification methods of 7 and 1 were also given.

■ A Facile One-Pot Synthesis of Model Diethyl 6,6'-Dioxotetrahydro-5,5'-bi(1,2,4-triazine)-5,5'-dicarboxylates

Mustafa M. El-Abadelah,* Hanan H. Mohammed, Mohammed M. Abadleh, Salim S. Sabri, and Firas F. Awwadi

*Department of Chemistry, Faculty of Science, The University of Jordan, Amman 11942, Jordan

Abstract

The reaction of diethyl aminomalonate with nitrile imine 1,3-dipolar species 1a,b follows a stereospecific path to deliver the racemic tetrahydro-6,6'-dioxo-5,5'-bi(1,2,4-triazine)-5,5'-dicarboxylates 4a,b, whilst the corresponding diastereomeric meso forms (5R, 5'S) could not be detected in the reaction product. Structural assignments for these novel heterocyclic dimers are based on microanalytical and spectral (MS, NMR) data, and further confirmed by X-ray diffraction analysis of single crystal for 4a.

■ One-Pot Three-Component Synthesis of 3,5-Disubstituted Isoxazoles by a Coupling–Cyclocondensation Sequence

Hai-Ling Liu,* Zhu-Feng Geng, Si-Yu Zhang, and Jie Han

*Analytical & Testing Center, Beijing Normal University, No. 19, XinJieKouWai St., HaiDian District 100875, China

Abstract

A convenient one-pot procedure for the synthesis of 3,5-disubstituted isoxazoles from acid chloride, terminal alkyne, and hydroxylamine hydrochloride catalyzed by Pd(PPh3)2Cl2/CuI has been developed. The coupling of acid chlorides to terminal alkynes afforded α,β-unsaturated ynones that underwent in situ cyclocondensation with hydroxylamines to afford the desired isoxazoles in 44–76% isolated yields.

■ Synthesis of 2-Arylbenzimidazole Analogues

Meng-Yang Chang,* Chieh-Kai Chan, and Yi-Chia Chen

*Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, TaiwanNo. 100, Shih-Chuan 1st Rd., San Ming District, Kaohsiung 80708, Taiwan, R.O.C.

Abstract

Substituted 2-arylbenzimidazoles (4) were easily synthesized in good yields starting from the condensation reaction of 1,2-diaminobenzenes (1) with β-ketosulfones (5) in the presence of boiling HOAc.

■ New Gallic Acid Glycosides from Mallotus plicatus

Kongsin Luangruangrong, Boonchoo Sritularak, Vimolmas Lipipun, and Kittisak Likhitwitayawuid*

*Department of Pharmacognosy, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Phayathai Road, Pathumwan, Bangkok 10330, Thailand

Abstract

From the stem bark of Mallotus plicatus (Müll.Arg.) Airy Shaw, two new gallic acid glycosides, namely bergenin-8-O-α-L-rhamnoside (1) and seco-bergenin-8-O-α-L-rhamnoside (2) were isolated along with seven known compounds (3-9). The structures of the new isolates (1 and 2) were elucidated through analysis of their 1D- and 2D-NMR, and MS spectral properties, as well as chemical evidence. seco-Bergenin-8-O-α-L-rhamnoside (2) and protocatechuic acid (7) showed weak inhibitory activity against Herpes simplex virus, whereas the other compounds were devoid of such activity.

■ New Monoterpenoid Indole Alkaloids from Gelsemium elegans

Wei Zhang, Sheng-Yuan Zhang, Zhi-Qi Yin, Lei Wang,* and Wen-Cai Ye*

*Institute of Traditional Chinese Medicine and Natural Products, College of Pharmacy, Jinan University, 601 West Huangpu Avenue, Guangzhou, 510632, China

Abstract

Three new monoterpenoid indole alkaloids, 18, 19-dihydro-21-oxokoumine (1), 14-hydroxygelselegine (2) and Nb-methyl-19, 20-dihydrorankinidine (3), together with five known alkaloids (4-8) were isolated from the roots of Gelsemium elegans. The structures with absolute configurations of the new compounds were elucidated on the basis of HR-ESI-MS, NMR, CD spectra analysis and single crystal X-ray diffraction.

■ Isoindolone Synthesis via Intramolecular Coupling of Benzylic C-H Bonds with Amide N-H Bonds

Ming Zhang,* Tianbao Chen, and Qinhua Liu

*College of Chemistry, Jiangxi Normal University, 99 Ziyangdadao, Nanchang, Jiangxi, 330022 , China

Abstract

Four 7-methyl-2-(8-quinolinyl)-2,3-dihydro-1H-isoindol-1-ones were synthesized from 2,6-dimethyl-N-(8-quinolinyl)benzamides with exellent yields using Pd(OAc)2 as a catalyst, iodobenzene as an oxidant and AgOAc as an additive.