| Abstract: | Attempted Synthesis of Nonafulvenes and of Nonaheptafulvalene The reaction of cyclononatetraenide with α-bromobenzyl acetate ( 6 ) as well as with 1,1-dihalodimethylether gives at ?50°, instead of the expected cyclononatetraenes, bicyclo[6.1.0]nona-2,4,6-triene derivatives 10d and 16 (Scheme 3 and 5, respectively). It seems that in some cases the well known thermally disrotative valence isomerization of cyclononatetraenes 7 to 3a, 7a-dihydroindenes 8 is much slower than the formation of bicyclo[6.1.0]nona-2,4,6-trienes of the type 10 and 16 . This type of reaction hurts the Woodward-Hoffmann rules. Possible precursors of the attractive nonaheptafulvalene are prepared by reaction of acetoxy-tropylium fluoborate ( 19a ) as well as of bromo-tropylium bromide ( 19b ) with lithium-cyclononatetraenide (Scheme 8). So far, the attempted gas-phase pyrolysis of the precursors 21a and 21b failed to give nonaheptafulvalene (5). |
