O-Aminobenzophenones

The importance of the configuration of the oxime is again demonstrated in the oxidative cyclization of o-aminobenzophenone oximes. The (Z)-oxime with nitrous acid produced 3-phenyl-l,2-benzisoxazole, while the (E)-oxime with similar treatment yielded ben-zotriazine N-oxides (27CB1736). 

When o-aminobenzophenone is heated with formamide in the presence of formic acid at 150°C for 20 min, a quantitative yield of 4-phenylquinazoline is obtained. In the absence of formic acid longer heating is necessary. Although this reaction does not proceed with o-acylamidobenzophenones, its extension to other o-acylanilines with aliphatic amides may prove fruitful. 

The reduction of a dinitro ketone to an azo ketone is best achieved with glucose. 2,2 -Dinitrobenzophenone treated with glucose in methanolic sodium hydroxide at 60° afforded 82% of dibenzo[c,f [i 2]diazepin-l 1-one whereas lithium aluminum hydride yielded 24% of bis(o-nitrophenyl)methanol [575], Conversion of aromatic nitro ketones with a nitro group in the ring into amino ketones has been achieved by means of stannous chloride, which reduced 4-chloro-3-nitroacetophenone to 3-amino-4-chloroacetophenone in 91% yield [178]. A more dependable reagent for this purpose proved to be iron which, in acidic medium, reduced m-nitroacetophenone to m-aminoacetophenone in 80% yield and o-nitrobenzophenone to o-aminobenzophenone in 89% yield (stannous chloride was unsuccessful in the latter case) [903]. Iron has also been used for the reduction of o-nitrochalcone, 3-(o-nitrophenyl)-l-phenyl-2-propen-l-one, to 3-(o-aminophenyl)-l-phenyl-2-propen-l-one in 80% yield [555]. 

Taylor and Heindel reacted several substituted o-aminobenzophenones and o-aminoacetophenones with DMAD the yields of the quinolones produced depend on the basicity of the starting amino compounds. They also reacted isatoic anhydrides (360) with DMAD in basic methanolic medium to obtain 4-quinolones (361).393... 

The availability of o-benzoylbenzenesulfonyl chlorides, prepared by diazotization of o-aminobenzophenones followed by reaction with sulfur dioxide in the presence of cuprous ions, can be exploited in the reaction with hydrazine or methylhydrazine to give 1,2,3-benzothiadiazine 14. Product 14 (R1 = Me) can also be obtained by methylationof 14(R = H) with methyl iodide and sodium hydroxide. The reduced form 15 results from catalytic hydrogenation of 14 (R = H, R2 = H)(68JHC453). Hydra-zobenzene reacts with 2-chlorosulfonylbenzoyl chloride in the presence of triethylamine to give diphenyl derivative 16 (79MI1). 3,1,2-Benzothia-... 

The 1,4-benzodiazepinones, exemplified by diazepam (53), undergo hydrolysis in acid and base to yield the corresponding o-aminobenzophenones (54). However, unusual byproducts were observed when diazepam (53) or 2-((V-methyl)amino-5-chlorobenzophenone (54) was hydrolysed in aqueous methanolic hydrochloric acid, and now a mechanism involving a nitrene has been proposed to account for the... 

A one-step synthesis of ( )-rutacridone (37) was achieved by the reaction of acridone (32 R = H) with isoprene dibromide isorutacridone (36), the isomer with linear annelation, was a minor product of the reaction (Scheme 5).19 A full account of the synthesis of acronycine from o-aminobenzophenones has now appeared (c/. Vol. 7, p. 90) and a modified route has been described (Scheme 6).20 Cyclization of the benzophenone derivative (38 R = Me) gave acronycine (39) (38%) and isoacronycine (40) (38%) a similar ring-closure of compound (38 R = H) furnished des-iV-methylacronycine. 

When reaction of jy -isomer of substituted o-aminobenzophenone oxime with chloroacetyl chloride was performed under Shotten-Baumann conditions, it failed to stop on the formation of 2-chloroacetamide intermediate 99 (see Equation (14), Section 14.08.7.1.3 <2001MI140>) and spontaneously formed 1 //-bcnzo[//][ 1,2,6]oxadiazocin-2(3//)-one 100 <2003KGS485>. 

Arylanthranils have been reduced with a new palladium catalyst to o-aminobenzophenones 348 lithium aluminum hydride gives the corresponding o-aminobenzhydrols in good yield.349... 

Tecleanone (55), the first o-aminobenzophenone to be isolated from a natural source, is a constituent of Diphasia klaineana, Teclea verdoomiana, and T. grandifolia. ° The structure assigned to tecleanone was based on the spectral data, fragmentation in the mass spectrometer into the ions (A) and (B) being particularly... 

Nearly a century ago, Posner obtained a material of empirical formula C7H5N from zinc chloride-catalyzed reduction of o-nitrobenzaldehyde. The compound, probably arising from intermediary o-aminobenzalde-hyde, was assigned either structure 137 or 114 (R = H) (1898CB658). [Compound 114 (R = H) has never been accessible from o-aminobenzal-dehyde for its synthesis, see Section II,C,2.] At about that time, Sond-heimer reacted o-aminobenzophenone with hydrochloric acid and obtained 6,12-diphenyldizenzo/6 //-1,5-diazocine (138, R-R6 = H)... 

Oxidative cyclization of o-aminoacylbenzenes is a much less common process for the synthesis of anthranils than the reductive cyclizations discussed in the previous section, mainly because the o-aminoketones are in many instances best prepared by reductive ring opening of anthranils (see Section III,C,3). Nevertheless, a few examples have been recorded. Oxidation of o-aminobenzophenones to the nitroketones using peroxytrifluoro-acetic acid, permaleic acid, or persulfuric acid proceed via the 3-phenyl-anthranil which occasionally is isolable.168 Caro s acid is also a useful oxidant.169... 

In contrast, oxidation of o-aminobenzophenone with lead tetraacetate under a variety of conditions yields only azo compound.171 However, the... 

The base-catalyzed reaction of benzyl cyanides with p-chloronitro-benzenes is widely used as a preparative route to 3-arylanthranils (Eq. 8), and hence, by reductive ring opening, o-aminobenzophenones, the valuable precursors of the pharmacologically important benzodiazepinones. By this method 3-phenylanthranils bearing trifluoromethoxy,173 (trifluoromethyl)-thio,173 sulfonamido,174 methoxy- and ethoxycarbonyl,175,176 cyano,175 methylsulfonyl,175 halo,176 difluoromethoxy,177 and acetyl (protected as the... 

Photolysis of 3,5-diphenylanthranil in concentrated hydrochloric acid produces 5-(p-chlorophenyl)-2-aminobenzophenone as expected from a consideration of mesomeric structures (165 R1 = Ph).228 5-Halogeno-3-phenylanthranils under similar conditions yield 3,5-dihalogeno-2-amino-benzophenones, whereas photolysis in concentrated sulfuric acid results in substitution (by hydroxy) and migration of the halogen to give 2-amino-6-halogeno-5-hydroxybenzophenones in 25-35% yield. Irradiation of 3-phenylanthranils in hydrobromic acid is somewhat different in that unsubstituted o-aminobenzophenones are produced in addition to their bromo derivatives.228... 

Dihydro-l//-l,4-benzodiazepin-2-ones 21 are obtained from o-aminobenzophenones by a cyclocondensation with amino esters under base catalysis or by A -acylation with halo acid chlorides followed by cyclization with ammonia ... 

Starting from o-aminobenzophenone (X) the following reactions are carried out ... 

Regarding the latter self-condensation, various substituted o-aminobenzophenones condense to afford 6,12-diaryldibenzo[6/][l,5]diazocines in often excellent yield (Equation (13)) <868324, 88JHC459, 89JHC1611, 90JIC48). 

Under thermal or base catalytic conditions, an o-aminobenzophenone fails to react with simple ketones such as cyclohexanone and deoxybenzoin (67JHC565). Zolfigol et al. have very recently discovered that o-aminobenzo-phenones react with simple ketones such as cyclohexanone and deoxybenzoin in the presence of SSA as a solid protic catalyst under MW conditions to yield new quinolines bearing hindered substituents. To show the powerful effect of SSA in the synthesis of quinolines with bulky substituents, the reaction of deoxybenzoin with 6-chloro-2,3,4-triphenylquinoline 1... 

Beier and Pastyrikova (13MI411) reported that reductive ring opening of SFs-substituted benzisoxazoles 78a, 79a using iron in aqueous AcOH resulted in excellent yields of ori/ o-aminobenzophenones 100, 101, which can be used as precursors for the synthesis of other SFs-substituted heterocycles such as quinazoHnes (see Section 2.8), as weU as for the synthesis of SFs-substituted quinolines. Thus 6-SFs-quinoline 102 was prepared in high yield by the Friedlander annulation reaction of 101 with excess ethyl acetoacetate in the presence of catalytic cerium (IV) ammonium nitrate (CAN). Similarly, aminoketone 100 was condensed in good yield with cyclohexanone to provide 7-SFs-quinoline 103 (Scheme 25). 

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