Indoxazenes, reduced

Closure of Bonds 1—7a and 3—3a Indoxazene derivatives are also accessible by 1,3-dipolar cycloaddition of nitrile oxides or nitrones to suitable dipolarophiles. Minisci and Quilico55 obtained the 3-phenyl compound by addition of benzo-nitrile oxide to benzyne [Eq. (4)]. The method is more widely applicable to the preparation of reduced indoxazenes, which will be dealt with later (Section II, D). 

The reaction of enamines with nitrile oxides, forming hexahydro-(76) and tetrahydro- (77) indoxazenes,105 has been used to prepare indoxazenes and naphthoisoxazoles, by dehydrogenating the reduced derivatives using A-bromsuccinimide.340 Addition of cyanogen di-A-oxide to cyclohexa-1,4-diene gives di-3a,4,7,7a-tetrahydro-... 

Cycloadditions involving nitrile oxides are normally associated with the production of reduced indoxazenes (see Section II,D). However, with benzyne as the dipolarophile, 3-substituted indoxazenes may be prepared.27... 

The O-acetate of 3-methyl-5-nitrobenzophenone oxime on thermolysis at 165°C under reduced pressure (20 mm) yields 5-methyl-7-nitro-3-phenyl-indoxazene (78%).28 The 5-methyl-6-nitro isomer is prepared similarly. 

As mentioned in Section II,C,2,b, attempts to reduce 3-(o-aminophenyl)-indoxazene with lithium aluminum hydride result in rearrangement to 3-(o-hydroxyphenyl)indazole. The rearrangement is equally successful with sodium hydride in boiling tetrahydrofuran and proceeds via the amine anion as shown in Eq. (3).29... 

Fully reduced indoxazenes are best prepared by 1,3-dipolar cycloaddition of nitrones to cyclohexenes112 and to cyclohexanone enamines.113-115... 

Of the reduced indoxazenes, attention is drawn to the hydrazide of 4,5,6,7-tetrahydroindoxazene-3-carboxylic acid which, as the hydrochloride, is more potent than iproniazid as an inhibitor of mitochondrial monoamine oxidase.126... 

Other uses of reduced indoxazenes include the antibacterial and antiprotozoal activity of 3-(5-nitro-2-furyl)-3a,4,5,6,7,7a-hexahydro derivatives,127... 

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