Benzoxazoles derivatives

An analogous ring contraction occurs in the reaction of the methylsulfanyl compound 3 with morpholine to give the benzoxazole derivative 4.37... 

Interestingly, it was also found that A -acetyl-A -arylnitrenium ions cyclize to form protonated benzoxazole derivatives (34). This reaction was found to have barriers of 4-11 kcal/mol in the gas phase. Although this finding has yet to be verified experimentally, it is significant in view of the fact that these nitrenium ions are frequently used in mechanistic studies of DNA damage. 

Nitromethane also reacts with arenediazonium tetrafluoroborates to give phenol, arene and benzoxazole derivatives,244 whereas radical-chain hydrodediazoniation occurs in dioxane when atmospheric oxygen is not strictly excluded.245... 

The microwave-assisted synthesis of a benzoxazole derivative by the same approach was also described starting from 2-aminophenol (Scheme 3.17)29. 

The benzoxazole derivative 19, with an activated methylene group, gave pyrido[2,l-6]benzoxazole (20) with DMAD,480 initial attack presumably having taken place on the nitrogen atom. 

A thiourea derivative CGP 6140 (32) [54], developed by Ciba-Geigy represents a new class of compound, which shows significant macrofilaricidal activity at 50-100 mg/kg in a variety of animal models. The further extension of this work generated two more new compounds, benzothiazole and benzoxazole derivatives (CGP 20376 and CGP 24914) which both possess potent micro- and macrofilaricidal activities [55], However, CGP 20376 has also been found orally effective against Brugia infections at a dose of 6.25 mg/kg [38]. Further studies with these compounds in the treatment of onchocerciasis and other filarial infections are currently under evaluation. 

Selective ERa and ER(3 receptor modulators consisting of triphenylethylenes, (n), and naphthyl benzoxazole derivatives, (III), were prepared by Kaltenbach (3) and Malamas (4), respectively, and used in treating estrogen-stimulated diseases such as breast, uterine, and ovarian cancers. 

Quniazolyn-4-[3H] and benzoxazole derivatives were also prepared by the author as illustrated in Eq.l and Eq. 2, respectively ... 

Methods for preparing 7-(p-C4H9-CioH2i alkoxyaromatic)-benzoxazole derivatives of Step 8 is described (3). 

By contrast, 2 mol of quinone were consumed in the productic of the benzoxazole derivative III (see Scheme 20.2). This is evidenced by the incorporation of a molecule of quinone II in III (in the benzoxazole unit) and the recovery of one additional mole of IV. In this process the a carbon of the carboxylic acid chain is oxidized from the stage of an amine to that of an imino ester. Compare Schemes 20.1 and 20.2. 

Chlorzoxazone is a centrally acting benzoxazole derivative with a weak muscle relaxing effect (1). It is usually used in combination with paracetamol for the treatment of painful muscle spasms. The usual dose is 500 mg tds. Drowsiness, weakness, dizziness, and gastrointestinal complaints are the most frequent unwanted effects. 

Anodic addition of an oxygen function to a C = N or C = C double bond may be exemplified by the oxidative cyclization of aryl semicarbazones to 1,3,4-oxadiazoles in acetonitrile-acetic acid containing H2SO4 or, under strictly anhydrous conditions (in the presence of acetic anhydride), to triazolinones [40]. Other examples are the anodic oxidation of benzaldehyde-2-hydroxyanil to 2-phenyl-1,3-benzoxazole derivatives [41] and the indirect oxidation of 2-hydroxychalcones to flavonoids using tris(4-bromophenyl)amine in MeOH-CH2Cl2 as mediator [42] ... 

The principal photochemical process on irradiation of the benzoxazole derivative (7) is reversible rra/i5,cw-isomerism. A photostationary state is established comprising 69% of the cis isomer. The rra j,c/5-isomerism of bis(2-... 

Chlorzoxazone, a benzoxazole derivative with skeletal muscle relaxant properties (250 to 750 mg p.o. t.i.d.), is used as an adjunct medication in the treatment of acute and painful musculoskeletal conditions. 

Table XVll.D-1 lists the distribution of oxazole- and oxazine-related compounds identihed in tobacco and tobacco smoke. A total of fifty-six compounds have been identified nine are benzoxazole derivatives, four are isoxazole derivatives, thirty are oxazole derivatives, four are oxazolidine derivatives, and nine are morpholine derivatives. Fourteen of the compounds are found in tobacco, forty-four are found in tobacco smoke, and two are found in both tobacco and tobacco smoke. Table XVII.D-2 lists the fifty-six oxazole-and oxazine-related compounds identified in tobacco and tobacco smoke.

Phenylarsolane is converted into the 1-chloroarsolane by heating in a bomb reactor (Equation (45)) <70ZAAC(377)278>. 1,3-Benzoxazole derivatives are prepared from 1,3-benzoxaphospholes and phenylarsine <84PS(20)347>. 

It should be noted that there is also a large body of literature on the photophysics of benzoxazole derivatives, which is outside of the scope of this review but clearly of relevance to those in the field. Leading references are provided for benzoxazole itself " and the widely studied oxazole yellow fluorescent dyes and their interactions with DNA strands. 

Coordination compounds of 2-hydrox3 henyloxazole are rarely studied, e.g., 350 (03CM4949). For a similar benzoxazole derivative, however, there are various metal complexes differing in the number of the chelate fragments. Mono-chelate coordination compounds include neutral platinum 351 (M = Pt, L = = Cl) (91BCJ149) and rhenium 352... 

Reproduced from Sharma H. Singh N, Jang DO. A ball-milling strategy for the synthesis of benzothiazole, benzimidazole and benzoxazole derivatives under solvent-free conditions. Green Chem 2014 16 4922-30, with permissbn from the Royal Society of Chemistry. 

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