Seminarji gostujočih znanstvenikov 2005/2006
Fakulteta za znanosti o okolju Univerze v Novi Gorici vljudno vabi na izredni seminar z naslovom "Interconversion of nitrenes, diradicals and ylides" prof. dr. Curt Wentrup-a (The University of Queensland, Brisbane, Australia), v ponedeljek 5. junija 2006, ob 15. uri v predavalnici P-5 Univerze v Novi Gorici. Seminar bo v angleškem jeziku.
Aromatic and heteroaromatic nitrenes undergo several interrelated unimolecular reactions: ring expansion to azacyclohepatetraenes or to a new class of bond-switch isomers which are zwitterionic cumulenes (cyclic nitrile ylides), ring opening to nitrile ylides, nitrile imines, diradicals or dienylnitrenes, and ring contraction to 5-membered ring nitriles.
2-Quinazolylnitrenes undergo diradicaloid and ylidic ring openings. Argon matrix photolysis of tetrazolo[1,5-a]quinazoline/2-azidoquinazoline affords 2-quinazolylnitrene, which has been characterized by ESR, UV and IR spectroscopy. A diradical is formed rapidly by ring opening and characterized by ESR spectroscopy; it decays thermally at 15 K with a half-life of ca. 47 min due to its facile intersystem crossing (triplet to open-shell singlet) followed by cyclization to 1-cyanoindazole and H-shift to N-cyanoanthranilonitrile.
Furthermore, benzotriazacycloheptatetraene can photochemically interconvert with the ring opened product, 2-isocyano--diazo--phenyltoluene as determined by IR and UV spectroscopy.