Seminars of invited scientists 2005/2006
School of Environmental Sciences University of Nova Gorica kindly invites you to the seminar "Interconversion of nitrenes, diradicals and ylides" prof. dr. Curt Wentrup (The University of Queensland, Brisbane, Australia), which will be held on Monday, 5 June, 2006 at 15.00 hours in lecture room P-5 at University of Nova Gorica.The seminar will be performed in English.
romatic 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.