Tropone oximes

Machiguchi, Nozoe and coworkers have very recently observed that in contrast to chemical reactivity of tropones, the tosylate of tropone oxime undergoes a facile ring-opening to 6-substituted (Z,Z,Z)-1,3,5-hexatriene nitriles on reaction with various nucleophiles305. For example, reaction of phenyl lithium results in the corresponding hexatriene carbonitrile (equation 183). 

Fused tropone oximes and arylhydrazones are formed on cyclizing 5-nitroso- or 5-arylazotropolones with bifunctional synthons (cf. Sections II,A,l,d and II,A,3,g). Among numerous further examples [e.g., 53MI2 57DOK(l 15)526 59NKZ1175], some reactions show specific features (Schemes 150-152). 

On treatment with hydroxylammonium chloride it is converted into tropone oxime, which is an example of a tropone imine [233]. 

Tropone oxime 493 cannot be efficiently obtained from the reaction between 16 and hydroxylamine, because the reaction gives mainly 2-aminotropone. However, if the reaction employs tropothione 491 as the starting material, 493 is produced in good yield. The contrast of the C - 2 attack of 16 and the C -1 attack of 491 is rationalized in terms of frontier orbital theory. The tosylate 494 derived from 493 reacts quite readily with a variety of nucleophilic reagents at low temperatures to give hexatriene derivatives 495 with (Z,Z,Z)-configuration in excellent yields (Scheme 6.130) [295]. 

Ai -A-homo-4-ketones by reaction with lithium and biphenyl at The resulting dienone is transformed into the corresponding tropone by treatment with bromine. The Swiss chemists also found that base treatment of 19-mesyloxy-A " -3-oximes gives directly 4-oximino-A-homo-estra-l(10),2,4a-trienes in moderate yield. ... 

Benzoxazoles are produced in high yield from a-acylphenol oximes by a Beckmann rearrangement using zeolite catalysts <95SC3315>. The reaction of the o-benzoquinone 40 with aromatic aldehyde oximes produces the benzoxazoles 41 <95ZOR1060>. The fused oxazolium salts 43 (R = Me, Et, Pr , or Ph R2 = Me or Pr ) are formed from tropone and nitrilium hexachloroantimonates 42 <96JPR598>. 

Just like tropone, oxepinotropone 374 (Scheme 100) with hydrazine gives the 9-amino compound 375a (and a small amount of the 7-amino isomer 375b), whereas treatment with hydroxylamine leads to 375a and the E- and Z-forms of the oxime [94H(38)957],... 

Other imino derivatives arise, as by-products or in side reactions, on heterocyclization. Thus, the treatment of cinnamoyltropolones 75 with hy-droxylamine (Scheme 19) yields, in the case of the 5-nitro derivative, the corresponding isoxazolotroponeoxime (89JHC371). The formation of oximes and several hydrazones from 3-acetyltropolone or its derivatives has also been mentioned (Section II,A,3,c). Moreover, an azine was obtained in addition to quinoxalotropone 213 (Section II,B,2,c) a tropone immonium salt was isolated after an extremely complex diene reaction of an 6-amino-2-azaazuIene (93CB441). 

Both the 2,3-benzo- and 4,5-benzo-tropones show marked alternation of bond lengths in their seven-membered rings [242]. It was early noticed that 4,5-benzotropone did not form an oxime or a phenylhydrazone [123]. 2,3-Benzotropone forms a 2,4-dinitrophenyl-... 

---