Chemotherapeutic agents. The structure of 1-(2-chloroethyl)-3-(4-carbamoylpyrazol-3-yl)-Δ²-1,2,3-triazolinium chloride

Abstract

A number of nitrogen mustards have shown significant activity in experimental tumors; however, many of them exhibit erratic behavior in clinical tests. The nitrogen mustard 5-[3,3-bis(2-chloroethyl)-l-triazeno]-pyrazole-4-carboxamide was found to undergo a spontaneous ring closure to form the compound 1-(2-chloroethyl)-3-(4-carbamoylpyrazol-3-yl)-A 2-1,2,3-triazolinium chloride, [CION6CaHI2] ÷ CI -, which shows no in vivo activity in experimental tumors. The structure of this ionic compound was determined by single-crystal X-ray diffraction techniques, using 1253 independent counter-collected reflections. A full-matrix least-squares refinement yielded a conventional R value of 0-0497. The space group is Pbca and the cell dimensions are a= 14.151 (5), b= 16-990 (5) and c= 10.344 (10) ~. The observed density of 1.489 g.cm -3 is consistent with 8 molecules per unit cell, de= 1.490 g.cm -3. The molecule contains a positively charged triazolinium ring with the chloride ion almost symmetrically located above the ring. The planes of the pyrazole and triazolinium rings make an angle of 50 ° while the amide group makes an angle of 22 ° with the pyrazole ring. The amide oxygen atom interacts with the triazolinium ring but on the side opposite to the chloride ion. Both pyrazole tautomers are present in the crystal.

Crystal and Electronic Structure of Stable Nitrenium Ions. A Comparison with Structurally Related Carbenes

“…Normally, carbenes 4a have a high tendency toward dimerization. ,,, A similar difference of p(π) at N(2) is observed between the saturated nitrenium ion 4d + (0.99) and the unsaturated 3d + (1.17). However, since the absolute value of the p(π) population at N(2) even for the saturated 4d + is comparatively high, it is not surprising that a nitrenium ion of this structural type, 17 + Cl - , Chart , has been isolated and structurally characterized even earlier (although its properties were not discussed in connection with stabilized nitrenium ions and carbenes) . We determined the X-ray crystal structure of the 1-methyl-3-phenyltriazolinium perchlorate 18 + ClO 4 -…”