No abstract

Five and six-membered cyclic 3-iodo enones undergo spiroannelation with symmetric internal acetylenes RCCR (R = Me, Et, n-Pr, and Ph) in the presence of NiBr, and zinc powder to afford spiro[4.4]nonadienones and spir0[4.!5]decadienones in good to excellent yields at temperatures of 60-100 O C . While NiBr, is a catalyst precursor, zinc powder acts as a reducing agent in the reaction. The observed catalysis is solventdependent, and best yields are obtained in acetonitrile or DMF. The addition of PPh, to these nickel-catalyzed reactions inhibits the rates and decreases the yields of spirodienone product. Palladium complexes PdCI, and PdCI,-PPh, are also active catalyst precursors for the spiroannelation. A mechanism is proposed on the basis of the well-established nickel and palladium chemistry to account for the observed catalysis. The proposed mechanism gains support from the observation that the oxidative-addition adduct of Pd(PPh,), with 3-iodo-2cyclohexen-lane reacts with 2 equiv of 3-hexyne to give the corresponding spirodienone in essentially quantitative yield. Summary:The dicarbonylation reaction of trans -pdeuteriostyrene to dimethyl 2-phenylbutanedioate and dimethyl 2,5-diphenyl-4-oxoheptanedioate using pd-(CF,C00),/2,2'-bipyridine as the =tabst precursor in the presence of 1,4-benzoquinone (Le., under conditions suitable for the formation of syndiotactic poly( 1 -phenyl-3-