- 3-pyridazinylnitrenes and 2-pyrimidinylnitrenes
-
Mild flash vacuum thermolysis of tetrazolo[1,5-b]pyridazines 8T generates small amounts of 3-azidopyridazines 8A (8aA, IR 2145, 2118 cm-1; 8bA, 2142 cm-1). Photolysis of the tetrazoles/azides 8T/8A in Ar matrix generates 3-pyridazinylnitrenes 9, detected by ESR spectroscopy (9a: D/hc = 1.006; E/hc = 0.003 cm-1). Cyanovinylcarbenes 11, derived from 4-diazobut-2-enenitriles 10, are also detected by ESR spectroscopy (11a: D/hc = 0.362; E/hc = 0.021 cm-1). Carbenes 11 rearrange to cyanoallenes 12 and 3-cyanocyclopropenes 13. Triazacycloheptatetraenes 20 were not observed in the photolyses of 8. Photolysis of tetrazolo[1,5-a]pyrimidines/2- azidopyridmidines 18T/18A in Ar matrices at 254 nm yields 2-pyrimidinylnitrenes 19, observable by ESR, UV, and IR spectroscopy (19a: ESR: D/hc = 1.217; E/hc = 0.0052 cm-1). Excellent agreement with the calculated IR spectrum identifies the 1,2,4-triazacyclohepta-1,2,4,6-tetraenes 20 (20a, 1969 cm -1; 20b, 1979 cm-1). Compounds 20 undergo photochemical ring-opening to 1-isocyano-3-diazopropenes 23. Further irradiation also causes Type II ring-opening of pyrimidinylnitrenes 19 to 2-(cyanimino)vinylnitrenes 21 (21a: D/hc = 0.875; E/hc = 0.00 cm-1), isomerization to cyaniminoketenimine 25 (2044 cm-1), and cyclization to 1-cyanopyrazoles 22. The reaction mechanisms are discussed and supported by DFT calculations on key intermediates and pathways. There is no evidence for the interconversion of 3-pyridazinylnitrenes 9 and 2-pyrimidinylnitrenes 19.
- Torker, Sebastian,Kvaskoff, David,Wentrup, Curt
-
p. 1758 - 1770
(2014/03/21)
-
- Reactions of Unsaturated Azides, 8. - Azidobutatriene and Azidobutenynes
-
When 1-azido-4-chloro-2-butyne (11), obtained from 1,4-dichloro-2-butyne (10), is treated with sodium hydroxide in methanol, 4-ethynyl-1H-1,2,3-triazole (19) is the main product besides the two triazoles 9 and 21.On the way from 11 to 19 and 21 azidobutatriene (14) most probably acts as a short-lived intermediate leading to five-membered heterocyclic compounds as azidoallenes do.In contrast to 14, the azidobutenynes 23 and 27 are relatively stable.They mainly give 2H-azirines (24, 28) on thermolysis and photolysis. - Keywords: Azidobutatriene, ring closure of; Triazole, preparation via azidobutatriene; Azirines
- Banert, Klaus
-
p. 1175 - 1178
(2007/10/02)
-
- Cobalt-Mediated Synthesis of Propargyl Nitriles and α-Alkoxy Propargyl Nitriles
-
Dicobalt hexacarbonyl complexes of propargyl acetates and acetylenic acetals couple efficiently with diethylaluminum cyanide to produce the corresponding complexed propargyl nitriles and cyanohydrin derivatives, respectively.A convenient procedure for preparing propargyl nitriles and α-alkoxy propargyl nitriles from propargyl alcohols and acetylenic acetals using this methodology is described.
- Stuart, John G.,Nicholas, Kenneth M.
-
p. 454 - 455
(2007/10/02)
-