Preparation and reactivity of some stable nitrile oxides and nitrones

a,b;g,d-Unsaturated nitrile oxides 6, 13 have been prepared from the corresponding aldehydes via sequential oxime formation, chlorination, and dehydrochlorination. These nitrile oxides show unexpected stability, presumably due to delocalisation, and can be isolated. 2,6-Diphenylbenzonitrile oxide 13b was particularly stable and a single crystal X-ray structure was obtained. 3,3-Diphenylpropenitrile oxide 6 was also isolated but could be dimerized, to give a 1,4,2,5-dioxadiazine 7 or furoxan 8, via slight modifications to the conditions employed. The corresponding nitrones 14, 17 have also been prepared, via the reaction of the a,b;g,d-unsaturated aldehydes 10a,b with substituted hydroxylamines, isolated and trapped.