Nitrene-carbene-carbene rearrangement. Photolysis and thermolysis of tetrazolo[5,1- a ]phthalazine with formation of 1-phthalazinylnitrene, o-cyanophenylcarbene, and phenylcyanocarbene

Martin Høj, David Kvaskoff, Curt Wentrup

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

1-Azidophthalazine 9A is generated in trace amount by mild FVT of tetrazolo[5,1-a]phthalazine 9T and is observable by its absorption at 2121 cm-1 in the Ar matrix IR spectrum. Ar matrix photolysis of 9T/9A at 254 nm causes ring opening to generate two conformers of (o-cyanophenyl) diazomethane 11 (2079 and 2075 cm-1), followed by (o-cyanophenyl)carbene 312, cyanocycloheptatetraene 13, and finally cyano(phenyl)carbene 314 as evaluated by IR spectroscopy. The two carbenes 312 and 314 were observed by ESR spectroscopy (D|hc = 0.5078, E|hc = 0.0236 and D|hc = 0.6488, E|hc = 0.0195 cm-1, respectively). The rearrangement of 12 â., 13 â., 14 constitutes a carbene-carbene rearrangement. 1-Phthalazinylnitrene 310 is observed by means of its UV-vis spectrum in Ar matrix following FVT of 9 above 550 C. Rearrangement to cyanophenylcarbenes also takes place on FVT of 9 as evidenced by observation of the products of ring contraction, viz., fulvenallenes and ethynylcyclopentadienes 16-18. Thus the overall rearrangement 10 → 11 → 12 â., 13 â., 14 can be formulated. © 2013 American Chemical Society.
Original languageEnglish
JournalJournal of Organic Chemistry
Volume79
Issue number1
Pages (from-to)307-313
Number of pages7
ISSN0022-3263
DOIs
Publication statusPublished - 2014

Keywords

  • Organic Chemistry
  • Diazomethanes
  • ESR spectroscopy
  • IR spectrum
  • Phthalazines
  • Ring contraction
  • Ring opening
  • Trace amounts
  • UV-Vis spectrum
  • Absorption spectroscopy
  • Photolysis
  • Organic compounds
  • 1 phthalazinylnitrene
  • carbenoid
  • o cyanophenylcarbene
  • phenylcyanocarbene
  • phthalazine derivative
  • tetrazolo[5,1 a]phthalazine
  • unclassified drug
  • article
  • electron spin resonance
  • infrared spectroscopy
  • photolysis
  • reaction analysis
  • ring opening
  • ultraviolet spectroscopy

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