1, 4, 5, 6‐Tetrahydro‐ν‐tetrazin‐Derivate

1, 4, 5, 6‐Tetrahydro‐ν‐tetrazin‐Derivate The title compounds 2 and 13 are readily available from α‐lithiated N‐alkyl‐nitrosoamines 1 (see Tables 1 and 2) which decompose at − 73° to yield the N‐oxides 2. The ESR. spectra of two derivatives 1 are recorded (Fig. 1), and tentative mechanisms are proposed for the head to head dimerizations ( la‐ 3‐ 4‐ 5‐ 2a and Scheme 1). Coupling of lithionitrosoamines with iodine (‐6) and alternative decomposition routes of representatives of this class of organometallics with special substitution [equations (2)‐(5)] are reported. The structures of the tetrazines are established by spectroscopic data [ESCA] (Fig. 2), IR., UV., 1 H‐ (cf. Fig. 9) and 13 C‐NMR., PE. (Scheme 2), by an X‐ray analysis of 2a (Fig. 4‐8 and Table 3), and by the chemical reactions. The crystal structure of 2a is a twisted boat with non planar terminal nitrogen atoms which reflects the electron repulsion in the 4‐atom‐6‐electron NNNN‐system. Comparisons are made with 2‐tetrazenes, the open chain analogues of 13 , wherever possible. Raney‐Ni reductions of 2 or 13 gives diamines 14 to which is assigned the d, l‐configuration through the 1 H‐NMR. spectra of the aminals 7 and 15 . Neither the oxides 2 nor the tetrazines 13 undergo cycloaddition reactions [equation (6) and Section 4]. Compound 2a is dimerized to the bis (nitrosoamino)‐2‐tetrazene 18 by treatment with acid, Zn II , Cu I or iodomethane. 2a is oxidized at nitrogen to the ethylene diamine derivative 6a (through 20 , with H 2 O 2 ), or at the CH 2 ‐groups of the ring to give oxo‐ N ‐oxide 21 (with MnO 2 or the ring contracted oxo‐tetrazoline‐ N ‐oxide 22 (with KMnO 4 ). Pyrolysis or photolysis of the dimethyl tetrahydrotetrazine 13a furnishes the trimer 26 of N ‐methylimine, but no diazetidine 27 . Silver and mercury complexes 29 are obtained from 13a , while Cr(CO) 5 . THF does not furnish a complex as with azocompounds, but rather replaces N 2 in 13a by CO (→ 28). Oxidation with permanganate converts 13a into the oxalic acid derivative 30 with unchanged tetrazine structure.