ChemInform Abstract: SYNTHESIS OF BENZOAXAZOLES, BENZOTHIAZOLES AND BENZIMIDAZOLES AND EVALUATION OF THEIR ANTIFUNGAL, INSECTICIDAL AND HERBICIDAL ACTIVITIES

Hisano, Takuzo; Ichikawa, Masataka; Tsumoto, Kazuyuki; Tasaki, Masanobu

doi:10.1002/chin.198307198

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“…Benzoxazoles are a useful class of heterocycle that have found prominence in the area of medicinal and agricultural chemistry. − Due to the preponderance of this motif in biologically active compounds, a number of methods have been developed for their synthesis − and functionalization . One underutilized method of benzoxazole formation is via the reaction of 2-aminophenols with nitriles .…”

Section: Introductionmentioning

confidence: 99%

Methods for the Direct Synthesis of Benzoxazoles from Halogenated Nitriles in Alcoholic Solvents

Lester

Camp

2013

ACS Sustainable Chem. Eng.

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NMR spectra …………………..…………………………………………S11 S2 I. General Experimental InformationUnless otherwise stated, all commercially available reagents and solvents were used without further purification.THF and DCM were dried over sodium/benzophenone and calcium hydride respectively, and purified by distillation prior to use. Toluene was dried by distillation. All anhydrous experiments were carried out in flamedried glassware. The solvents used for flash column chromatography were technical grade. For purification procedures using column chromatography, silica gel (60-120) mesh was used. Thin layer chromatography was carried out using Merck Kieselgel silica gel 60 F254 plates (0.2 mm) and visualisation was achieved using UV light followed by dipping in a potassium permanganate solution and heating. 1 H NMR and 13 C NMR were recorded on a JEOL 270 Mhz spectrometer at ambient temperature using CDCl 3 (7.27 ppm). Chemical shift values are expressed as parts per million (ppm) and coupling constants and are expressed in Hertz, followed by multiplicity indicated as s: singlet, d: doublet, t: triplet, q: quartet or combination, br.s broad singlet or m: multiplet. Solution IR spectra were recorded on a Perkin Elmer 1600 series FTIR-spectrophotometer.Microwave reactions were run in a Biotage Initiator 2.0 microwave and the reaction temperature was monitored by IR. Mass spectra were determined using a Bruker MicroTOF mass spectrometer. II. Synthesis of trichlorobenzoxazoles 2a-lGeneral procedure 1: To a stirred suspension of PtCl 4 (10 mol %) and 2-aminophenol (1 equiv.) in n-hexane (1 M) at rt was added trichloroacetonitrile (2.2 equiv.). The resultant mixture was stirred at 80 °C for 19 h. The solvent was removed under reduced pressure and the residue was purified by flash column chromatography on silica gel (3% ethyl acetate in petroleum ether) to afford the benzoxazole.General procedure 2: To a solution of 2-aminophenol (1 equiv.) in methanol (1M) at rt was added trichloroacetonitrile (1.1 equiv.). The resultant mixture was stirred at 40 °C for 19 h. The solvent was removed under reduced pressure and the residue was purified by flash column chromatography on silica gel (3% ethyl acetate in petroleum ether) to afford the trichlorobenzoxazole. 2-(Trichloromethyl)benzo[d]oxazole (2a) 1General procedure 1: PtCl 4 (18 mg, 0.05 mmol), 2-aminophenol (1a, 58 mg, 0.53 mmol), trichloroacetonitrile (117 µL, 1.17 mmol) in n-hexane (0.53 mL), afforded 2-(trichloromethyl)benzo[d]oxazole (2a, 102 mg, 82% yield) as a white solid. General procedure 2: 2-Aminophenol (1a, 233 mg, 2.14 mmol), trichloroacetonitrile (236 µL, 2.35 mmol) in methanol (2.14 mL), afforded 2-(trichloromethyl)benzo[d]oxazole (2a, 499 mg, 99% yield) as a white solid. N O CCl 3 2a S3

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Section: Introductionmentioning

confidence: 99%

Methods for the Direct Synthesis of Benzoxazoles from Halogenated Nitriles in Alcoholic Solvents

Lester

Camp

2013

ACS Sustainable Chem. Eng.

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ChemInform Abstract: SYNTHESIS OF BENZOAXAZOLES, BENZOTHIAZOLES AND BENZIMIDAZOLES AND EVALUATION OF THEIR ANTIFUNGAL, INSECTICIDAL AND HERBICIDAL ACTIVITIES

Abstract: Die Aniline (I) reagieren mit den Methylpyridinen bzw. 2‐Methylchinolin (II) in Gegenwart von Schwefel zu den Benzothiazolen (III).

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Methods for the Direct Synthesis of Benzoxazoles from Halogenated Nitriles in Alcoholic Solvents

Methods for the Direct Synthesis of Benzoxazoles from Halogenated Nitriles in Alcoholic Solvents

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