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The first representative of the 1,2,3,4-tetrazine-N-oxides, 5,7-dibromobenzo-1,2,3,4-tetrazine-1-N-oxide 4b, has been obtained by intramolecular reaction of o-(tert-butylazoxy)phenyldiazonium tetrafluoroborate 2b. Compound 4b has been characterized by NMR spectroscopy and an X-ray diffraction study and its transformation 4b→ 5b→ 6b investigated; o-azidonitrosobenzene 5b was isolated and characterized for the first time.

Benzo-l,2,3,4-tetrazine 1-N-oxide formation involves the intramolecular cyclization of 2-(tert-butyl-NNO -azoxy)phenyldiazonium tetrafluoroborates and the N→N migration of the tert-butyl group to afford 2-(tert-butyl)benzo-l,2,3,4-tetrazinium 4-N-oxides 3 followed by elimination of the tert-butyl group. Compounds 3 were hydrolysed to give a new heterocyclic system, viz. 2-alkyl-6-oxo-2,6-dihydrobenzo-l,2,3,4-tetrazine 4-N-oxides. For 2-(tert-butyl)-8-bromo-6-oxo-2,6-dihydrobenzo-l,2,3,4-tetrazine 4-N-oxide an X-ray diffraction study was carried out.

Monomeric isocyano complexes of rhodium(III) have been prepared from 1,2-dimethyl-3-isocyano- 2b and 3-isocyano-1,2-dicarba-closo-dodecaborane(12) 2a and rhodium dimer [(η5-C5Me5)RhCl2]2 1; the structure of the resulting carborane rhodium complex was determined by an X-ray diffraction study.

It has been shown that nucleophilic substitution in 6β-chloro-7,8-didehydro-4,5α-epoxy-3-rnethoxy-17-methylmorphinan and 8β-bromo-6,7-didehydro-4,5α-epoxy-3-rnethoxy-17-methylmorphinan is accompanied by allylic rearrangement with both a change in and retention of the orientation of the substituting group. X-Ray diffraction studies of 8α-phenyl-6,7-didehydro- 4,5α-epoxy-3-methoxy-17-methylmorphinan and 6β-phenyl-7,8-didehydro-4,5α-epoxy-3-rnethoxy-17-methylmorphinan have been carried out.