Ketoximes, ©-unsubstituted

The conversion of oxime 71 to imide 72 is a related but more complicated reaction104). The reduction of the oxime concurrent with migration finds analogy in the conversion of steroid ketoximes 74 to enimides 75 under identical conditions 105). The imide 72 may be hydrolyzed to arsaniline 73. It might also be noted that in the case of benzyl substituents 69 b and 71b the reactions take place with partial loss of substituent (to 70 c and 72 c). Thus, these procedures may be used to prepare the unsubstituted 4-arsaniline and 4-arsaphenol. 

Acyl halides with 3-unsubstituted indoxazenes give acylsalicylo-nitriles. The acyl group may be exclusively or chiefly in the ring (49) or on the oxygen atom (50). 3-Alkyl derivatives, on the other hand, form ring-acylated ketoximes (51), besides acylated indoxazenes.67... 

Unsubstituted ketoximes undergo rearrangement in nonacidic media also. Thus, both geometric isomers of cholest-4-en-3-one oxime (12) rearranged to (13) in the presence of triphenylphosphine in refluxing tetrachloromethane (equation 8) 7 the apparent reluctance to migrate of endocyclic unsaturated substituents has also been observed for 0-substituted oximes (vide infra). 

The action of cold thionyl chloride on salicylhydroxamic acids, and on o-hydroxyaldoximes and -ketoximes, is a versatile synthetic route to 3-hydroxy-, 3-unsubstituted, and 3-alkylindoxazenes.26... 

Rozenfeld investigated hetero-alkylated amines and urotropine hydroiodide, and found them to be more effective than the unsubstituted amines. Chlorinated amines were also investigated by Tamura et al. Recently, Tagmazyan et al. discovered that alkyl(2-hydroxyethyl)dimethylammonium bromides are effective corrosion inhibitors for steel in HCI. Aldoximes and ketoximes can also be very effective, according to Costain and Terry. ... 

The reaction smoothly proceeds also at 100°C in the presence of 30% (from ketoxime weight) KOH in DMSO in autoclave under initial acetylene pressure of 8-16 atm. The maximum pressure reached at the reaction temperature is 20-25 atm. Then, intensive consumption of acetylene begins, and pressure quickly decreases. As it was already noted, initially, N-unsubstituted pyrroles are formed, which further are vinylated in the presence of acetylene excess. If it is necessary to obtain the corresponding NH-pyrrole, the synthesis is carried out with calculated amount of acetylene or with its lack. LiOH appears to be a selective catalyst of the pyrrole ring construction, the application of which does not require strict dosing of acetylene. 

Later, it has been proven that the initial stage of the process is a 1,3-prototropic shift in O-vinyl oximes, primary intermediates of the reaction. Therefore, the early interpretation of regiodirectivity of the pyrrole synthesis, based on the idea about different reactivity of E- and Z-configurations of the starting ketoximes, needs correction. It is obvious that 1,3-prototropic shift in O-vinyl oximes will proceed easier with the participation of the methylene group and not the methyl moiety, because in the former case the disubstituted ethylene fragment of N,0-divinyl hydroxylamine A is known to be more thermodynamically stable in comparison with unsubstituted compound B (terminal vinyl group) (Scheme 1.104). 

At 60°C-80°C, the major reaction product is nitrogen-unsubstituted pyrrole. For example, a mixture of isomeric pyrroles in a ratio of 5.7 1 is obtained at 80°C. Thus, benzyl ethyl ketoxime reacts with acetylene predominantly through the methylene group of the benzyl radical. 

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