Hexaazapolycycles by Selective Multimethylenations with Dichloromethane and Base or with Hexamethylenetetramine Multiple methylenations of 2‐aminomethylbenzimidazole with dichloromethane and methylamine or ammonia or with hexamethylenetetramine lead to highly selective formations of 6 new single bonds to give only a polycyclic bis‐spiro‐1,5‐diazocine 2 or only a polycyclic spiro‐1,3,6‐triazonine 4 or only a polycyclic 1,3,6,8‐tetrazecine derivative 6. 4 and 6 may be equally well obtained starting with 2‐chloromethyl‐benzimidazole. All of these selectively formed products are concave cryptands with 6 amino nitrogen atoms. No template metals are used in their syntheses. The reasons for the unusual changes in selectivity are investigated using semi‐empirical PM3 calculations and mechanistic considerations. Experimental and spectroscopic details are given.

Im Eintopfverfahren sind die neuartigen Tetraazaheterocyclen 2 erhältlich, wenn man das Benzimidazolderivat 1 mit RNH2 in wasserfreiem Dichlormethan umsetzt (Raumtemperatur, Ausbeute ca. 60%). Die Verbindungen 2 sind potentielle Vorstufen für Tetraaza‐azulen‐Kationen und lassen wegen ihrer Verwandtschaft zu Pteridinen interessante biologische Wirkungen erwarten (R  H, Alkyl, Aryl).magnified image

The dienes 3 can be unequivocally characterized Hand 13C-NMR spectroscopically (Table 2). In contrast to 1aminomethyl-I ,3-butadiene derivatives, which have proven to be effective antimycotics,1'21 very little is known about compounds of type 3.113-161 So far, we have been unable to observe dimer formation as has been described for 2aminomethyl-I ,3-b~tadiene['~l and its quaternary ammonium salt. ['6] We are presently investigating whether other dienes 3 can be synthesized by substitution of 1 (e. g. 1 g), and whether the base-catalyzed reaction of DMSO with carbonyl compounds involves a generally applicable principle for the synthesis of dienes. ExperimentalA solution of KOtBu (5.9 g, 52 mmol) in DMSO (50 mL) was treated slowly with 52 mmol of 1 and the resulting mixture stirred for 12 h at 80°C. After cooling to room temperature the mixture was poured into ice-water, the organic phase separated off. and the aqueous phase extracted several times with ether. The combined organic phases were washed with saturated NaCl solution to remove residual DMSO and then dried over K,CO,. After removal of the solvent, the dienes 3a-d were isolated by distillation in vacuo.

In instrumental activation analysis, increasing use has recently been made of 2~2Cf spontaneous-fission neutron sources. Such a source has a neutron yield which is high and practically constant and is easy to work with. At the same time a 252Cf source is cheap enough for industrial laboratories where problems are often encountered which can be solved by means of a source containing about 1 mg of 252Cf.Owing to the large cross section of the {n, 7) reaction for many elements, activation by thermal neutrons is preferable if the matrix does not strongly absorb slow neutrons. For example, aluminum is such a matrix, and therefore some components and impurities in aluminum alloys can be determined with high precision with the aid of a simple 252Cf isotope source. Among the principal components of aluminum alloys, manganese has the greatest cross section for the (n, 3') reaction for thermal neutrons: aT(55Mn) = 13.3 + 0.2 b [1]. Therefore, manganese is the most suitable element for testing the possibility of using 252Cf.The aim of our present work was to estimate the accuracy, sensitivity, necessary irradiation and measurement times, etc., for the quantitative analysis of manganese in aluminum with a 660 #g 252Cf source, a 40 em 3 Ge(Li) detector (resolution 3.2 keV at 661.6 keV), and a Didak-4000 analyzer. The absolute efficiency of the Ge(Li) detector at 50-1400 keV was determined by means of calibrated 226Ra and 182Ta sources of the same dimensions as the specimen [2]. To moderate the fast neutrons we used a water tank 60 cm in radius and 80 em deep.To find the optimum irradiation site we investigated the fluxes of thermal, resonance, and fast neutrons in relation to the radial distance r and vertical distance Z from the source (Fig. 1). The fluxes of thermal and resonance neutrons were measured by means of Rh, Au, and In foils 63.0, 0.85, and 0.30-4.71 mg/cm 2 thick respectively. The integral fluxes of fast neutrons were measured by means of the threshold reactions llsIn(n, n'), 27Al(n, p), and 27Al(n, ~); the thicknesses of the indium and aluminum disks were, respectively, 290 and 620 mg/cm z. The diameters of the specimens were the same as those of the A1Mn alloy specimens. From the measured values of the fluxes of thermal and fast neutrons we obtained an approximate optimum for the irradiation in the range of TABLE 1. Quantity of Manganese in A1Mn Alloys, DeterminedbyVarious Methods, 10 -~

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