Benzoxazin-2-one

Poly(phenylquinoxaline—arnide—imides) are thermally stable up to 430°C and are soluble in polar organic solvents (17). Transparent films of these materials exhibit electrical insulating properties. Quinoxaline—imide copolymer films prepared by polycondensation of 6,6 -meth5lene bis(2-methyl-3,l-benzoxazine-4-one) and 3,3, 4,4 -benzophenone tetracarboxyUc dianhydride and 4,4 -oxydianiline exhibit good chemical etching properties (18). The polymers are soluble, but stable only up to 200—300°C. 

The enzyme catalyzes the hydrolysis of an amide bond linkage with water via a covalent enzyme-inhibitor adduct. Benzoxazinones such as 2-ethoxy-4H-3,l-benzoxazin-4-one [41470-88-6] (23) have been shown to completely inactivate the enzyme in a competitive and stoichiometric fashion (Eigure 5). The intermediate (25) is relatively stable compared to the enzyme-substrate adduct due to the electron-donating properties of the ortho substituents. The complex (25) has a half-life of reactivation of 11 hours. 

Treatment of 3-hydroxy-l,2-benzisoxazole with benzyl bromide gave a mixture of O-and iV-benzyl compounds. The iV-benzyl compound gave a benzoxazin-4-one on reaction with base, via the intermediates shown in Scheme 88 (78CPB549). 

Treatment of 7V-benzyl-l,2-benzisoxazolin-3-one with base produced a benzoxazine-4-one (see Scheme 88). The base catalyzed rearrangement of the 2-methyl-3-phenyl-l,2-benzoisoxolium salt to an oxazine is believed to proceed via a similar intermediate (67AHC(8)277). A number of other decompositions could possibly proced via this proposed route (74HCA376, 67AHC(8)277), which has also been postulated for the rearrangement of a variety of isoxazolium salts, e.g. the conversion of (200) into (202) (Section 4.16.3.3.2(i)(b)). 

Benzoxazinones pyrolysis, 3, 998 Benzoxazinones, dihydro-benzazetidine formation from, 7, 277 Benzoxazin-4-ones, dihydrosynthesis, 3, 1028... 

Reaetion of l,3-benzoxazin-4-ones (43, 44) or trithioisatoie anhydride (45) with amidrazones (46, 47) or thiosemiearbazide (48) resulted in the formation of 3-(l-amidino)- (49-51) and 3-(l-thioureido)pyrimidines (52) respeetively. Compounds 49-52 underwent thermal intramoleeular ey-elization to the eorresponding l,2,4-triazolo[l,5-c]quinazolines (53-56) [68CB2106 76MI1 80PHA582 83MI1 85H(23)2357] (Seheme 18). 

Chiral 2,2-disubstituted l,3-benzoxazin-4-ones as auxiliaries in the synthesis of carbapenem antibiotics 97YGK858. 

Cycloaddition of 2-styryl-4/7-3,l-benzoxazines and malononitrile gave 1 -amino-3-aryl-2-cyano-1 //,6//-pyrido[l, 2-n][3, l]benzoxazin-4-ones (99ZN(B)923). These tricyclic derivatives were also prepared in the reaction of 2-methyl-4//-3,l-benzoxazin-4-one and arylidenemalononitrile in AcOH in the presence of NaOAc. 

Amino-3,l-benzoxazin-4-one was reacted with diethyl malonate in the presence of sodium hydride in dimethylformamide at ambient temperature for 4 hr to give 4-quinazolinylidenemalonate (546) in 28% yield [83JCS(P1)813],... 

Organolithium additions to 2-phenyl-3,3-dimethyl-3//-indole (37), followed by oxidation of indolines (38) with m-chloroperoxybenzoic acid, gave indolinic aminoxyls (39) in 20-30% yield. The organolithium addition does not occur when groups other than phenyl are present at C(2). Attempts to synthesize suitable precursors such as 1,2-dihydro-2-phenyl-2-alkylbenzothiazole, 1,2-dihydro-2-phenyl-2-alkylbenzoxazole, and l,2-dihydro-2-phenyl-2-alkyl-4//-3,l-benzoxazin-4-one for other new aminoxyls failed. 

Two types of dihydro-l,3-oxazinones are relevant to the discussed topic the e -fused hexahydro-2//-l,3-benzoxazin-4-ones and their homologs, and the d -fused hexahydro-2//-3,l-benzoxazin-4-ones and their homologs. For the synthesis of these derivatives, just two methods are known. 

Nucleophilic olefins react readily with trichloroacetyl isocyanate to give l,3-oxazin-4-ones. In this way, norbornadiene 188 yields the 5,8-methano-2//-l,3-benzoxazin-4-one 189 (69JOC633). A similar 1,4-addition starting... 

Nohira et al. treated N-acylamino acids 195 with thionyl chloride mixed anhydrides 196 were formed below 30°C. The latter compounds gave the first type of hexahydro-2//-3,l-benzoxazin-4-one 197 on triethylamine treatment [77H(7)301]. This reaction was also performed with diexo- and diendo-substituted j8-amino acids 198 yielded the 5,8-methano-2//-3,l-benzoxazin-4-ones 199 via the acyl derivatives 200 (84S345,84T2385). Further homologs were also prepared by the dehydration of N-acylamino acid derivatives (85MI1 88MI3). 

Conformational Equilibria in Several cw-Fused HEXAHYDROCYCLOPENr[e][l,3]oxAziN-4-ONES (n = I), Hexahydro-2//-1,3-benzoxazin-4-ones (n = 2), 0CTAHYDR0CYCL0HEPT[e][l,3]0XAZIN-4-0NES (n = 3) AND Octahydroquinazolin-4-ones (n = 2) o... 

In another paper, the main El fragmentation processes of three pairs of diexo- and diendo-iased l,4,4a,5,8,8a-decahydro-5,8-methano-2//-3,l-benzoxazin-4-ones 374 (91IJM225 91MI2) were established by means of mass spectrometry and MNDO calculations. The El mass spectrometric fragmentations of the bis-oxazinones 375 have also been reported [79ACH(101)61]. 

The constitutionally isomeric 3-substituted (l//,3//)-quinazoline-2,4-diones and 2-phenylimino-4//-3,l-benzoxazin-4-ones are easy to distinguish via their El mass spectra (93RCM374). For quinazolinediones, the most striking feature is the loss of CO2, proving that a rearrangement due to anilino migration must occur. 

Reversing the CH=N group position in 477-5,6-benzoxazin-4-one should result in the same isomerization enthalpy as from HC(NMe)OMe to MeCHNOMe. The enthalpy of formation of the latter species was calculated to be —7.1 kJmoR from the high-level quantum chemical calculations of Reference 4. The enthalpy of formation of the former species is unknown. However, if we accept the gas phase isomerization enthalpy of dimethylamides to methyl imidates (69.6 13.4 kJmoR ) in equation 52 from Reference 75,... 

Chandrasekhar and colleagues used Af-acyl-Af, 0-bis(ethoxycarbonyl)hydroxylamines in a similar procedure to prepare amines. Aromatic Af-hydroxyimide derivatives were used by Marzoni and Varney " and Giitschow " to synthesize benz[crf]indol-2(l//)-one and 1-benzoxazin-4-one derivatives, respectively, via Lossen rearrangements. Both Af-benzyloxy and A-mesyloxy derivatives were used. 

The synthesis of quinazoline derivatives by ring-opening and ring-closure reactions involving isatoic anhydrides and 3,l-benzoxazin-4-ones is covered in Section 8.02.9.2. 

H and NMR studies on 477-3,l-benzoxazin-4-one derivatives 12 and their acylanthranilic acid precursors 13 led to the conclusion that differentiation between these two series of compounds was best achieved through the characteristic coupling interactions in the high-frequency carbonyl region <2000SAA1079>. 

Reformatsky reactions of Af-(2-bromoalkanoyl)-l,3-benzoxazin-4-ones 267 and 272 and imines derived from aniline or /)-substituted anilines gave fra j -/3-lactams 273 with complete diastereoselectivity, and the l,3-benzoxazin-4-one auxiliary 269 could also be recycled. However, in the similar transformations of imines containing an o-methoxyphenyl substituent on the nitrogen, no cyclization to azetidinone occurred and /r -/3-aminocarboxamide derivatives 274 were the only products formed (Scheme 51) <2005S725>. 

In the thermal cyclization of 3-alkoxyphenyl A -(l-aryl-2,2,2-trifluoroethylidene)carbamates 287, obtained from 3-alkoxyphenols 285 and l-aryl-l-chloro-2,2,2-trifluoroethyl isocyanates 286, 2-aryl-2-trifluoromethyl-2,3-dihydro-477-l,3-benzoxazin-4-ones 290 were formed instead of the regioisomeric l,3-benzoxazin-2-ones 288 (Scheme 53). The formation of 290 was explained by a thermal isomerization of 287 involving a skeletal 1,3-rearrangement of the electron-rich aryloxy group to the azomethine carbon, which is electron deficient due to the electron-withdrawing CF3 group <2002JFC(116)97>. 

Trimethylsilyl)salicylyl chloride 342, prepared in situ starting from salicylic acid 341 by using a two-step procedure, proved to react conveniently with diphenylimine under very mild conditions to form 2,3-diphenyl-2,3-dihydro-42/-l,3-benzoxazin-4-one 343 (Scheme 63) <1997JHC681>. 

The gallium(lll) triflate-mediated condensation of anthranilic acid with fluorinated ketones gave the corresponding 2,2-disubstituted l,2-dihydro-4//-3,l-benzoxazin-4-ones in high yields <20070L179>. 

The thermally induced cyclization of A -(benzyloxycarbonyl)phenyl ketenimines 415, obtained in a two-step, one-pot procedure from benzyl 2-azidobenzoates 414, led to 2-substituted-4/f-3,l-benzoxazin-4-ones 416 (Scheme 79). The reaction involves the formation of a new carbon-oxygen bond and migration of the benzyl group from the oxygen atom to the terminal carbon atom of the ketenimine fragment <2005S2426>. 

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