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# Cyclization of Polyalkene-1,1-dicarbonitriles Upon Direct Excitation and Photoinduced Electron Transfer to a Pyrylium Salt ## Klaus-Dieter Warzecha and Martin Demuth* Max-Planck-Institut für Strahlenchemie, P.O. Box 101365, D-45413 Mülheim an der Ruhr, Germany ### 1. Introduction. Photoinduced electron transfer from isoprenoid polyalkenes to the excited state of suitable electron acceptors in the presence of nucleophilic solvents has proven as an intriguing approach to initiate cascades of regioselective functionalization and subsequent radical cyclizations en route to new mono- and polycyclic compounds [1-6]. Among the polyalkenes examined, 1,1-dicarbonitriles such as 1, 2 and 3 constitute a class of special interest. Both direct irradiation of these readily available compounds, as well as electron transfer to acceptors absorbing at higher wavelengths, namely 2,4,6-triphenylpyrylium tetrafluoroborate (P+BF4-), give rise to synthetically useful products in high yields. Fig.1 Polyalkene-1,1-dicarbonitriles