3- -benzoxazol-2-one

In 1900, ultraviolet data were used to show that benzoxazol-2-one... 

In contrast with the hitherto described silylation-aminations of six-membered heterocycles, silylation-amination of five-membered hydroxy-N-heterocycles such as benzoxazol-2-one 289 with excess benzylamine and HMDS 2, to give 2-benzyla-minobenzoxazole, fails, because of the equilibrium between 2-trimethylsilyloxy-... 

Synthetic use can be made of the potent electrophilic properties of ADC compounds by transforming the initial adducts into heterocyclic products. For example, reaction of DEAZD with enamine 92 gives the substitution product 93 in quantitative yield. Further treatment of this initial adduct with acid, followed by base hydrolysis leads to benzoxazol-2-ones. The dimethyl substituted enamine (92, R = Me) gives the rare, but isolable 6//-benzoxazol-2-one ring system (Scheme 13).147... 

CASRN 66441-23-4 molecular formula C16H12CINO5 FW 333.70 Soil Hydrolyzes rapidly in soil forming fenoxaprop acid, ethyl alcohol, 6-chloro-2,3-dihydro-benzoxazole-2-one, and 4-(6-chloro-2-benzoxazolyloxy) phenol (Wink and Luley, 1988). Under aerobic and anaerobic conditions, the half-life was less than 24 h (Humburg et al., 1989). 

The tetrahydro-derivatives of the oxazole and isoxazole system are unstable. As a consequence, only acyclic products have been reported from the reductions with complex metal hydrides. 2,5-Diphenyl-oxazole (119) gave 2-benzylamino-l-phenylethanol (120),141 and 3,5-diphenyl-2-isoxazoline (121) was converted to 3-amino-l,3-diphenylpropanol (122)142 on reduction with lithium aluminum hydride. 3-Phenylbenzisoxazole was resistant to reduction with lithium aluminum hydride and sodium borohydride,143 but benz-oxazole (123), benzoxazol-2-one (124), and benzoxazol-2-thione (125) have been reported 141 to yield 2-methylaminophenol (126) on reduction with lithium aluminum hydride. 

The preparation of 3-H-benzoxazol-2-one from o-ami-nophenol and urea is well known but the reaction is accompanied by the formation of tars and other side reactions. In contrast, phosgene reacts cleanly with o-aminophenol. We have devised a simple process without any acid scavenger which affords pure benzoxazolone in excellent yield as depicted in scheme 183 (Ref. 236). 

Benzoxazoles. - Both o- and m-halogenobenzanilides (413) are converted into the amidines (415) by potassium amide in liquid ammonia these are formed by aryne cyclization to 2-phenylbenzoxazole (414) and subsequent aminoly-sis." The conversion of acetophenone oxime into 2-methylbenzoxazole by the action of phosphorus oxychloride involves a Beckmann rearrangement. Pyrolysis of aryl azidoformates, ArOaCNa, gives benzoxazol-2-ones. The azide (416) is converted into the benzoxazole (417) on heating. The... 

Much research interest in the synthesis of carbazoles is directed at the preparation of natural products. The total syntheses of murrayafoline A 153 and murrayanine have been reported <04S2499>. The key step included a regioselective cycloaddition between oxazolidinone 150 and acrolein which led to benzoxazol-2-one 151 after DDQ oxidation. Ring opening of the oxazol-2-one ring of 151 followed by methylation provided A-phenylaniline 152. A palladium-catalyzed intramolecular cyclization of the latter then produced the natural product 153. Finally, venerable iron-mediated chemistry has been utilized in the total synthesis of furoclausine A 154 <04SL528> and 6-chlorohyellazole 155 <04SL2705>. 

The clusters [FePd2(CO)4(jU-dppm)2] (24) and [Fe2Pd2(CO)s(NO)2(yU-dppm)2] (25) have been used as precursors to silica-supported heterogeneous catalysts for the transformation of o-nitrophenol to benzoxazol-2-one.l - l (Eq. 3). 

Hydrolysis of Benzoxazol-2-ones Followed by Oxidative Cyclization (Pd[II])... 

Tamariz et al. developed an access to 1-methoxycarbazoles 225 via hydrolysis of 3-arylbenzoxazol-2-ones 223 and subsequent palladium(II)-mediated oxidative cyclization of the resulting diarylamines 224 (Scheme 54) [213, 214]. The required benzoxazol-2-ones 223 are obtained by regioselective Lewis acid-catalyzed Diels-Alder reaction of 4,5-dimethylene-3-aryl-l,3-oxazolidm-2-ones with alk-enes followed by aromatization using 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ). 

Scheme 54 Synthesis of 1-methoxycarbazoles 225 by hydrolysis of the benzoxazol-2-ones 223 and subsequent palladium(II)-mediated oxidative cyclization of the diarylamines 224...

This sequence has been used for the synthesis of 6-methoxymurrayanine (232) (Scheme 55) [214]. Reaction of butane-2,3-dione (226) with 4-methoxyphenyl isocyanate (227) to 4,5-dimethylene-3-(4-methoxyphenyl)-l,3-oxazolidin-2-one (228) followed by regioselective boron trifluoride-catalyzed Diels-Alder reaction with acrolein afforded the oxazolone 229. Only minor amounts of the undesired regioisomer were formed. Aromatization using 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) afforded the benzoxazol-2-one 230. Saponification of the cyclic carbamate and subsequent O-methylation led to the diarylamine 231. Finally, oxidative cyclization using stoichiometric amounts of palladium(ll) acetate provided 6-methoxymurrayanine (232). 

Recently a heterogeneous Fe Pd catalyst derlyed -from a FePd2 cluster decomposed on silica, has been succes-fully employed for the carbonylat ion o-f ortho-n i trophenol to give benzoxazol-2-one, which is a structural element o-f herb cidesjsoidj, ... 

Table 89. Minimum Inhibition Concentrations (MIC) of 3-(3-Iodopropargyl)-benzoxazol-2-one (9.7) and 3-(3-Iodo-propargyl)-6-chloro-benzoxazol-2-one (9.8) in Nutrient Agar...

Compound 37 is probably derived from the insertion of CO into a Ru-N bond of an intermediate nitrene complex, followed by cyclisation with the -OH group to form benzoxazol-2-one. It is known [61, 62] that the reaction of Ru3(CO)i2 with azoarenes under CO results in the cleavage of the N=N bond to give Ru3(NPh)2(CO)9 and Ru3(NPh)(CO)io. The nitrene intermediate may lead to benzoxazol-2-one by w/ra-molecular attack of the nitrogen lone pair on an adjacent CO, followed by addition of the phenolic group to -NCO (Scheme 9) ... 

Benzoxazol-2-one is a structural element of herbicides and has a high synthetic potential. The catalyst derived from FePd2(CO)4(DPPM)2 (DPPM = bis(diphenylphosphino)methane) deposited on Si02 and dried at 450 °C for 16 h effects the reductive carbonylation of o-nitrophenol (38) to the benzoxazolone (37) at 200 C and initial CO pressure of 200 atm (eq. 15) [66, 67] ... 

The high reactivity of N-aLkyl-2-halogenobenzoxazolium salts allows attack at weakly nucleophilic functionaHties. Thus, ketones of the type Ar-CH2-CO-R are transformed to aUcynes by 4 [279] in a formal dehydration process with transfer of the C=0 oxygen to the heterocycle due to formation of the benzoxazol-2-one 6 (presumably via intermediates 5 and 7) ... 

Preparation by treatment of 4-benzoyl-2,3-dihydro- / =i/ benzoxazol-2-one (SM) with refluxing 20% hydro-... 

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