Synthesis of 5- and 7-(dicyanomethylene)-2,3-dihydrocyclohepta-1,4- dithiins, 'push-pull' heptafulvene derivatives. 8,8-Dicyanoheptafulvenes from α-bromomalononitrile and cycloheptatrienylium salt

Article abstract of DOI:10.1246/bcsj.66.3742

Treatment of 2,3-dihydro-4aH-cyclohepta-1,4-dithiin with triphenylmethyl tetrafluoroborate followed by condensation with α-promomalononitrile in pyridine afforded 5- and 7-(dicyanomethylene)-2,3-dihydrocyclohepta-1,4- dithiins in good yields. When changing the solvent to acetonitrile, the products obtained were 5- and 6-(2,2-dicyanoethyl)-2,3-dihydro-1,4- benzodithiins. This new method was applicable to the general synthesis of dicyanoheptafulvenes from tropylium salts.