The synthesis of several
seven-membered cyclic hydroxamic acids has been
carried out in low yield. Reduction of diethyl 2-hydroxyiminoheptane-l,7-dioate
afforded ethyl 1-hydroxy-7-oxohexahydroazepine-2-carboxylate, together with
related acyclic products. The cobactin precursor
3-bromo-1-hydroxyhexahydro-azepin-2-one was obtained
by the ring expansion of 2-bromocyclohexanone with benzenesulphonohydroxamic
acid and also by the peracid oxidation of 6-bromo-7-ethoxy-3,4,5,6-tetrahydro-2H-azepine. The methyl and cinnamyl
imidates of hexanolactam
were oxidized by peracid to
1-hydroxyhexahydroazepin-2-one, in addition to the related imino-
and nitroso-hexanoic esters. In a similar reaction, 1-hydroxypiperidin-2-one was obtained from 2-methoxy-3,4,5,6-tetrahydropyridine. During the course of these
oxidation reactions, the intermediate oxaziridines 7-methoxy-8-oxa-1-azabicyclo[5,1,0]octane and 6-bromo-7-ethoxy-8-oxa-1-azabicyclo[5,1,0]octane were isolated and identified.
The peraoid oxidation of ethyl N-cyclohexylbenzimidate yielded cyclohexylhydroxylamine and ethyl benzoate in reasonable
yields. This reaction suggests a useful method for the conversion of a primary
amine into the related hydroxylamine.
Synthetic Studies on Aphidicolane and Stemodane Diterpenes. III. An Alternative Stereoselective Access to Aphidicolane-Type B/C/D-Ring System.