A Diaziridine Imine

Abstract

Although increasing attention [2,31 has been paid to aziridinones and diaziridinones since the first discovery of an alactam "1, the analogous imines have so far been unknown [4I. Compounds of this type would be interesting in respect of their behavior on thermolysis [2* 51 and as possible intermediates in the rearrangement of N-haloguanidines to sernicarbazide derivatives [6*6al. We now report the first synthesis of a diaziridine imine and some of its properties.In the few cases studied, the action of hypochlorite on N,N',N"-trisubstituted guanidines has given only very unstable N-haloguanidines [71. However, from two moles of N,N,N"-tri-tert-butylguanidine (1) [81 and one mole of fert-butyl hypochlorite in carbon tetrachloride or n-pentane we obtained smoothly (80-85 % yield) the diaziridine imine (3) alongside one mole of ( I ) . HCl.The triple bond in (2) has a bond angle that deviates from 180° and thus causes severe ring strain. As a result, the -C =C-stretching vibration that is strictly forbidden on symmetry grounds appears in the IR region, so that, e.g., (2b) gives a weak band at 2155 cm-1; that this is really the vibration of the triple bond is shown by a very strong band at 2153 cm-1 in the Raman spectrum; this is comparatively broad and lies at longer wavelengths than for tolane (2220 cm-I), which again is an indication of the increase in ring strain due to the angled substituents [**I.The UV spectrum of diyhenylacetylene typec31 [(2b): Amax = 332 nm, E = 280001, which is much shifted to longer wave lengths, can be explained only on similar grounds.Further proofs of the structure of (2) are provided by the NMR (Varian HA-100) and mass spectra (LKB 9000). The methyleneprotons of (6) and (7) give a singlet at 6 = 2.95 and 3.09 ppm, respectively, and are thus magnetically equivalent, but for (2b) there are two multiplets at 8 = 2.35 and 3.20ppmwith Jgem = 11 Hz. The reason for the large chemical shift between the geminal methylene protons is the molecular distortion on conversion of (7) into (2b). whereby one proton is caused to lie in the plane of the neighboring benzene ring while the other is transferred to above the -C =C-bond. Bromine (16 g, 0.1 mole) is added dropwise, with stirring, to 5,6-dihydro-2,3,8,9-tetramethoxydibenza[a,e]cyclooctene (7) (32.6 g, 0.1 mole) 121 in benzene (325 ml). The solution becomes almost colorless within a short time. The benzene is distilled off in a vacuum, the residue is dissolved in ethyl acetate, and the solution is filtered from a small amount of a red decomposition product. Crystallization in the cold affords (lb) (42.7 g, 88 %). m.p. 173 "C.A solution of potassium (15.6 g, 0.4 mole) in tert-butyl alcohol (400 ml) is treated with 1-methylpiperazine (150 g) and then diluted with anhydrous ether (250 ml). Compound (Ib) (48.6 g, 0.1 mole) is then added and the whole is stirred for 3 days at room temperature. The mixture is then evaporated to dryness without removal of the precipitate and the residue is freed from potassium bromide by repeated treatment with water...

Opening the aziridinimine ring: a theoretical study

“…In other words, the ring-ring isomerization apparently constitutes the slower step of the two-step rearrangement [eqn. (2)], in agreement with the experimental observations mentioned above.…”

“…Using the calculated value mentioned above for 1, we could thus estimate an upper limit for the energy barrier of ca. AE* = 120 kJ mol-' for the [2 + 11 cycloreversion of trimethylaziridinimine. This value is consistent with the experimental values AM = 112-128 kJ mol-' derived by Quast et aL6 from kinetic measurements on a series of alkyl substituted molecules.…”

“…The latter corresponds to the process illustrated in eqn. (2). The open planar structure lE/lE is often postulated in the literature as an intermediate for various isomerization reactions.…”