Reaction of methyl 3,3-diazido-2-cyanoacrylate (1) with amines 2 at -30°C yields aminovinyl azides 4. In the presence of equivalent amounts of triethylamine the vinyl azides 4 undergo 1,Y-ring closure to afford the triethylammonium salts 5. Treatment of 5 with hydrochloric acid gives the corresponding 4,5-dihydro-lH-tetrazo1-5-ylidene derivatives 6. In contrast thermolysis of 4 leads via azirines 7 to oxazoles 8. Reaction of vinyl diazide 1 with lysine and cystine, respectively, yields bis(viny1 azides) 9. Triethylamine-induced 1,5'-ring closure of 9 produces the bis(triethy1ammonium) salts 10, which can be transformed under acidic conditions into the corresponding bis(4,5-dihydro-lH-tetrazol-5-ylidene) derivatives 11. With methyl acrylate (
Reaction of tetrazolyl enolate 2 (HL2) with Cu(II) acetate yields the 3D‐coordination polymer 4 ([CuL22]n). the structure of which is unequivocally established by single‐crystal X‐ray diffraction. The formation of 4 is understandable if 2 or its enolate is considered as tridentate chelate ligand and if an intermediate formation of the coordinatively unsaturated copper(II) building block 6 is assumed. The monomers 6 are bidentate coordinating by the two CN groups, which leads to linking of monomers and to coordinative saturation at the copper(II) center of 6 with formation of three‐dimensional 4. Semicorrin 8 (HL4), however, reacts with Fe(II) to give the exceptional mononuclear tetrahedral chelate complex 10 (X‐ray). EPR and Mössbauer spectra of 4 and 10 are discussed.
Reaction of 3,3‐diazido‐2‐cyanoacrylate 5 with four moles of ammonia gives tetrazolyl‐bisammonium salt 7. The key‐intermediate is the amino‐vinyl azide 6 which spontaneously undergoes a 1,5′ ring‐closure reaction followed by double deprotonation. Treatment of 7 with hydrochloric acid yields the parent of 2‐(4,5‐dihydro‐1H‐tetrazol‐5‐ylidene)‐2‐cyanoacetate 9 (R = Me, Et) as the only tautomer. Regiospecific monoalkylation of bisammonium salt 7a with dimethyl sulfate and reaction of ammonium salt 12 with hydrochloric acid gives (E)2‐(1‐methyl‐4,5‐dihydro‐1H‐tetrazol‐5‐ylidene)‐2‐cyanoacetate (13) (X‐ray structure of derivative 14). Compound 13 can also be obtained from vinyl azide 10 and methylamine. This experiment as well as AM1 calculations of 9a, 23 and 24 strongly favour tautomer 9a.
8] X-ray crystallographic data for (SS,5R,6S,7S)-2 (C,,H,,N02S): space group P2,2,2,, a = 933.2(2), b = 1060.2(2), c = 2136.2(5) pm, V = 2.1135(8) nm', Z = 4. = 1.180 gem-,, p(MoK,,) = 0.071 mm-I. Of 1593 independent retlections, 1534 with IF1 > 3 4 F j were considered for the solution of the structure and refinement. The anisotropic refinement converged at R = 0.0400. Refinement according to Rogers [9] yielded q = 0.9(3) and thus also the correct configuration.
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