1-SUBSTITUTED 1,3-DIHYDROISOTHIANAPHTHEN-2,2-DIOXIDES - PREPARATION AND USE AS ORTHO-QUINODIMETHANE PRECURSORS IN INTRA-MOLECULAR CYCLOADDITIONS - PRELIMINARY COMMUNICATION

1,3‐Dihydroisothianaphthen‐2,2‐dioxide 1 was readily converted to the 1‐substituted sulfones 3 by deprotonation and subsequent electrophilic attack (Scheme 3 and Table). The appropriate 1‐alkenyl‐ and 1‐alkenoyl‐sulfones 3 on heating at 213° to 240° underwent SO2‐extrusion to give, via the non‐isolated (E)‐quinodimethanes II (Scheme 1), polycyclic products such as 4, 6 and 7 in good yields (Schemes 4 and 5). On the other hand, thermolysis of the 1‐alkenoyl‐1‐thioether sulfones 9 furnished mainly the isochromenes 10 (Scheme 6). Copyright © 1979 Verlag GmbH & Co. KGaA, Weinheim