Preparation of phenyl substituted propargylic alcohol dicobalt hexacarbonyls and their reactions with active methylene compounds in the presence of acid

Eight new complexes with the formula [PhC_2C(OH)R^2R^2]Co_2(CO)_6 were prepared from phenyl substituted propargylic alcohols and dicobalt octacarbonyl.The reactions of these propargylio alcohol complexes with active methylene compounds,2,4-pentanedione or ethyl acetoacetate,in the presnce of an acid,HBF_4(40％)+P_2O_5(in excess)or BF_3·Et_2O,at room temperature in dichlorome- thane were investigated.From the 1-alkyl substituted tertiary propargylic alcohol complexes,three new conjugated ene-yne complexes produced by intramolecular dehydration reaction were isolated in high yields(82—95％).On the other hand,four new alkylated complexes were obtained with satisfactory yields(44—66％)from the secondary propargylic alcohol complexes.The influence of other acids,phosphorus pentoxide and polyphosphoric acid,on both dehydration reaction and alkylated reaction was also studied.