NMR Studies on [2 + 3] Cycloaddition of Nitrile Oxides to Polyunsaturated Medium Size Rings

Site selectivity, regioselectivity and stereoselectivity of [2 + 3] cycloaddition of 4-trifluoromethylbenzonitrile oxide to polyunsaturated medium size rings including 1,5,9-cyclododecatriene, 11-membered sesquiterpenes, 1,3-cyclooctadiene and 5-vinyl-2-norbornene were examined. Site selectivity was correlated with electron charges of alkenyl carbon atoms. Structure of the products has been established by an extensive application of 1D and 2D 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and electrospray ionization mass spectrometry. Some of the obtained products showed moderate fungicidal activities