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

Abstract

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 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy and electrospray ionization mass spectrometry. Some of the obtained products showed moderate fungicidal activities.

The influence of the structure of various isoxazole derivatives on photosynthetic apparatus of tomato plants grown in the field and greenhouse. Effect of various stages of plant growth in different seasons

“…Structures of isoxazole derivatives showing fungicidal activity previously described by our group are displayed in Figure . Those compounds include amides: 4‐pyridine ( N ‐aryl)‐3‐aryl‐5‐isoxazolecarboxamides ( 4 , 5 ) (Gucma, Gołębiewski, & Michalczyk, ; Gucma, Gołębiewski, Morytz, Charville, & Whiting, ), 4‐pyridine‐3‐aryl (3‐alkyl)‐2‐isoxazoline‐carboxamides ( 8 , 9 ) (Gucma, Gołębiewski, & Michalczyk, ; Gucma, Gołębiewski, Morytz, et al, ), ( N ‐aryl)‐3‐aryl‐2‐isoxazoline‐5‐carboxamides ( 6 , 7 ) (Gucma & Gołębiewski, ), 3‐aryl‐2‐isoxazoline‐5‐carboxylic acid 10 (Gucma, Gołębiewski, & Michalczyk, ), 3‐aryl‐2‐isoxazoline‐ester derivatives: cycloadducts of 4‐trifluoromethylbenzonitrile oxide to methyl (2 E )‐3‐[(4 S )‐4‐(prop‐1‐en‐2‐yl)cyclohex‐1‐en‐1‐yl]prop‐2‐enoate 11 (Gucma, Gołębiewski, & Michalczyk, ), to methyl E ‐3‐bicyclo[2.2.1]hept‐5‐en‐2‐ylprop‐2‐enoate 12 (Gucma et al, ), and a cycloadduct of 4‐trifluoromethylbenzonitrile oxide to sesquiterpene C 15 trans , trans , trans ‐2,6,6,9‐tetramethyl‐1,4,8‐cycloundecatriene 13 (Gucma et al, ).…”

“…2-isoxazolinecarboxylic acid chlorides were prepared by the published procedures from the corresponding aldehydes, cf. Scheme 1 (Gucma, Gołębiewski, & Krawczyk, 2013;Gucma, Gołębiewski, & Michalczyk, 2016).…”