PREPARATION OF PYRYLIUM GAMMA-BENCHROTREN IC SALTS - SYNTHESIS OF THEFIRST ORGANOMETAL PYRYLIUM-SALTS WITH FUSED RINGS - NMR-STUDY AND APPLICATION TO THE SYNTHESIS OF NEW BENZENE CHROMIUMTRICARBONYL COMPLEXES

Diacetylation of benehrotrenic alkenes by acetic anhydride and weak Le wis acid (ZnCl2, BF3-OEt2) is reported. A series of gamma-benchrotreni c pyrylium salts is obtained together with the mono and the diacetylat ed products. The first organometallic fused rings pyrylium sails are o btained. In connection with the electron donating effect of the Cr (CO )(3) group, the influence of rings deconjugation on NMR data is discus sed. Finally the reaction of acyclic and cyclic gamma-benchrotrenic py rylium salts with nucleophiles is described. (C) 1997 Elsevier Science S.A.