3b 5 Further studies on the mechanisms of both the pho- toinduced and thermally driven isomerization will be re- ported along with a more comprehensive study of the Diels-Alder reactivity of these new 1-phenylseleno 1,3- dienes. ... Acknowledgment. Financial support was provided by NSERC of Canada in the form of operating grants (MDF and GSB) and by the Alfred P. Sloan Foundation (M. DF). Supplementary Material Available: Experimental details, 'H NMR spectra, and ...