ACID-CATALYZED CARBONYLATION OF LACTONE TO CYCLIC ANHYDRIDE ON TUNGSTEN METAL

Facile carbonylation of the cis-vinyl complex Cp(CO)(3)W[CH=CH(COMe)] (2, Cp = eta(5)-C5H5) followed by cyclization affords the gamma-lacton e complex Cp(CO)(2)W[eta(3)-CHCHC(Me)OC(O)] (4). Further carbonylation of 4 induced by the presence of acid in CH3CN gives the cyclic anhydr ide complex Cp(CO)(CH3CN)W[eta(3)-CHCHC(Me)C(O)OC(O)] (9). The reactio n of 4 with Me2NH causes ring opening to yield the zwitterionic comple x Cp(CO)(2)W[eta(2)-Me2N=C(Me)CH=CHCOOH] (6). The cyclic anhydride lig and of 9 remains unchanged when 9 is treated with nucleophiles. For ex ample, the reaction of Me2NH with 9 affords the imine-coordinated comp lex Cp(CO)(Me2NC(Me)=NH)W[eta(3)-CHCHC(Me)C(O)OC(O)] (14), and the rea ction of NaBH4 with 9 generates the amine-coordinated complex Cp(CO)(M eCH2NH2)W[eta(3)-CHCHC(Me)C(O)OC(O)] (15). The structures of 4, 6, 9, and 14 have also been determined by X-ray diffraction analysis. The al lylic ligand in 9 is in an endo conformation.