Synthesis of azaheterocycles from oxime derivatives

Abstract

Electrophilic amination of Grignard reagents has been accomplished by using O-sulfonyloximes as amination reagents. Benzophenone O-sulfonyloxime derivatives react with Grignard reagents on sp2 nitrogen, yielding primary amines by successive hydrolysis of the resulting N-alkylimines. Various cyclic imines are synthesized by Pd-catalyzed reaction from olefinic oxime derivatives. That is, treatment of O-pentafluorobenzoyloximes of olefinic ketones with a catalytic amount of Pd(PPh3)4 and triethylamine affords nitrogen-containing heterocycles, such as pyrroles, pyridines, isoquinolines, spiro-imines, and aza-azulenes. This reaction proceeds via the initial formation of alkylideneaminopalladium(II) species generated by oxidative addition of the oximes to the Pd(0) complex, and the following intramolecular amination on the olefinic moiety. Cyclic imines are prepared from γ,δ-unsaturated O-acetyloximes by treatment with acetic acid and 1,4-cyclohexadiene in the presence of a catalytic amount of 1,5-naphthalene-diol. γ,δ-Unsaturated ketone O-methoxycarbonyloximes are transformed to 2-bromomethyl-3,4 dihydro-2H-pyrroles by the action of a catalytic amount of Cu(I) bromide dimethyl sulfide complex and lithium bromide.