Vinylindenes and some heteroanalogues in the Diels-Alder reaction. II. Substituted fluorenes from 3-vinylindenes

3-Vinylindene, 2-methyl-3-vinylindene and 3-isopropenylindene give normal, photostable adducts with ethenetetracarbonitrile by a Diels- Alder process. The first diene gives adducts with maleic anhydride, N- phenylmaleimide and dimethyl acetylenedicarboxylate. Where there is stereochemical ambiguity the adducts are shown by mass spectrometry to be exclusively endo. Two heterocyclic analogues are formed from 3- vinylindene with p-toluenesulphonyl cyanide and N-sulphinyl-p- toluenesulphonamide.