Syntheses and configurations of some heterocyclic amidoximes. X‐Ray crystal structure of 3‐phenyl‐5,6‐dihydro‐2(1H)‐pyrazinone‐O‐methyloxime

Abstract

O‐Methyl‐α‐ketophenylacetohydroximoyl chloride (1) was prepared by the reaction of O‐methyl‐α‐methoxyphenylacetohydroximoyl chloride (5) with N‐bromosuccinimide and concentrated hydrobromic acid. Reaction of 1 with ethylenediamine gave 3‐phenyl‐5,6‐dihydro‐2(1H)‐pyrazinone‐O‐methyloxime (6). 3‐Phenyl‐5,6‐cyclohexano‐5,6‐dihydro‐2(1H)‐pyrazininone‐O‐methyloxime (7) was prepared by reaction of 1 with trans‐1,2‐diaminocyclohexane. The X‐ray structure of 6 has been determined. The crystals are orthorhombic, space group Pbca with a = 10.264(3), b = 18.262(4), c = 23.530(4)Å, V = 4411(2)Å3, and Z = 16. The structure, which was refined to R = 0.038 using 1652 observed reflections, shows the amidoxime moiety to be the Z configuration. Reaction of benzohydroximoyl chloride with aziridine gave (Z)‐aziridinylbenzaldoxime (16a). Ultraviolet irradiation of a benzene solution of 16a gave a mixture of the Z and E isomers 16a and 16b. The E isomer 16b underwent thermal isomerization to 16a at 100°. Reaction of 16a with dimethyl sulfate in sodium hydroxide solution gave (Z)‐O‐methylaziridinylbenzaldoxime (17a). Photoisomerization of a hexane solution of 17a gave a mixture of the Z and E isomers 17a and 17b which were separated by preparative glc. The isomers 17a and 17b are resistant to thermal Z = E isomerization. The mechanisms of thermal isomerization of benzamidoximes are discussed.

A Facile Synthesis of N-Alkoxyacylimidoyl Halides from α-Nitro Ketones and Alkyl Halides in the Presence of NaHSO4/SiO2

“…Although several methods for the synthesis of N-alkoxyimidoyl halides have been reported, only one report describes the preparation of N-alkoxyacylimidoyl halide (3); 3 (X = Cl) was prepared from α-methoxyphenylacetonitrile in four steps (Scheme 1, b), namely, (1) amidoxime was prepared from the reaction of α-methoxyphenyl acetonitrile with hydroxylamine; (2) alkylation of amidoxime was carried out in order to obtain O-methyl-α-methoxyphenyl acetamidoxime; (3) the latter was then converted into the hydroximoyl chloride by nitrosative deamination in the presence of chloride ion; (4) the final step was the transformation of the α-methoxy group into a ketone functional group by reaction of the hydroximoyl chloride with N-bromosuccinimide (NBS) in the presence of a small amount of concentrated hydrobromic acid. 10 In this report, 3 was considered as a potential precursor for the preparation of heterocyclic compounds because it contains two functional groups that can react with nucleophiles at the same time. Applicability of this useful synthetic precursor, 3, will be extended if more simple synthetic methods for 3 are developed.…”