1,3-DIPOLAR CYCLOADDITION OF DINITRONES - FORMATION OF TRICYCLIC DIMERS

Various dialdehydes (1-5) were formed by addition of dithiols to acrol ein. Reaction of these dialdehydes with N-alkylhydroxylamines afforded dinitrones the two nitrone groups of which were joined by an alkylide ne chain containing two sulfur atoms (6a,b-10a,b). Cycloaddition of th ese dinitrones with dimethyl acetylenedicarboxylate proceeded in the u sual way giving bis(4-isoxazolines) (11a-15a). However, analogous dini trones formed by reaction of the dialdehydes with N-(4-tert-butyl-phen yl)hydroxylamine could not be isolated. Instead tricyclic compounds ar ose in which the central macrocyclic ring is flanked by two isoxazolid ine rings (16c-20c). Obviously, the dinitrones formed as intermediates underwent dimerization with formation of the tricyclic compounds by c ycloaddition between two nitrone groups and two tautomeric N-hydroxyen amine moieties. Two of the tricyclic compounds (16c and 20c) formed 1: 1 complexes with NiCl2 and FeCl3, respectively.