Gas-phase thermolysis of pyrazolines. 4. Electronic structure and gas-phase thermolysis of 4-substituted 3,3,5,5-tetramethyl-3,5-dihydro-4H-pyrazoles studied by photoelectron spectroscopy. First evidence for an alkylideneselenirane.
In: Tetrahedron (Tetrahedron), Jg. 52 (1996) ; Nr. 6, S. 1965-1980
Zeitschriftenaufsatz / Fach: Chemie
The electronic structures of the tetramethyldihydropyrazoles [(I; R=Se,S:O, NNH2, NN:CMe2) and II] have been studied by photoelectron spectroscopy and interpreted with the aid of semi-empirical SCF MO calcns. (PM3). Gas-phase pyrolyzes of I and II have been carried out and analyzed by photoelectron spectroscopy. Both I(R =Se, S:O) and in part I(R=NNH2) eliminate mol. nitrogen to form reactive species which cyclize to three-membered rings, i.e. the novel alkylideneselenirane III, the alkylidenethiirane S-oxide IV, and the cyclopropanone hydrazone V, resp., which decomp. at higher temps. The elusive alkylideneselenirane III was studied by IR spectroscopy in an argon matrix at 10 K.