The olefins mentioned in the title were copolymerized with CO in the presence of palladium catalysts modified with dicyclohexyl{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}phosphine. Productivities up to 95 g/(gPd · h) were achieved. The obtained copolymers were recovered in the pure, regio- und stereoregular polyketone structures 3 . The isotactic poly[2-benzyl-1-oxopropane-1,3-diyl] ( 3a ) and its analogues 3b , c were found to isomerize to the corresponding spirocyclic poly[3-(arylmethyl)tetrahydrofuran-2,2-5,5-tetrayl-2-oxy-2-methylene]s 4 in a suspension in CHC13, thus indicating that the spiroketal structure is thermodynamically the most stable for these copolymers. However, the atactic material did not undergo any structural transformation. These results show that regularity at the centers of chirality in the main chain is a prerequisite for the conversion of the polyketone to the spiroketal structure.