Catalyst for the carbonylation of oxiranes

A process for preparing lactones by catalytic carbonylation of oxiranes using a catalyst system comprising

• a) at least one carbonylation catalyst A comprising uncharged or anionic transition metal complexes of the formula (I)
• (Mα(n+))m[Mβ(L)4]l (I)
• where
• Mβ Re, Co, Ru, Rh, Fe, Ni, Mn, Mo, W or mixtures thereof with the formal charge −1,
• L is PR3, P(OR)3, NR3, SR2, OR2, CO, R—CN, R—NO2, (RO)(R′O)C═O, (R)(R′)C═O, (R)C═O(OR′),
• Mα is a metal of group 1 or 2 of the Periodic Table of the Elements, Zn or Hg, bis(triarylphosphine)iminium, trityl or T(R)4 where
• T is N, P or As,
• R and R′ are each, independently of one another, H, alkyl, aryl, alkaryl or aralkyl,
• n and m are each 1 or 2 and
• l is n×m and
• b) at least one chiral Lewis acid B of the formula
• LnMXm
• where
• M=Mg, Ca, Sc, Y, rare earth element, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, TI, Pb, which are present in coordinatively unsaturated form under the reaction conditions,
• X=halide, sulfate, sulfite, nitrate, nitrite, carboxylate, sulfide, phosphate, sulfonate, borate,
• L(n)=phosphine, cyclopentadienyl or ansa-ligands, salen, imines, oxazoline, alkoxide, phenoxide, carboxylate, where various L can also be joined to to one another and L is chiral,
• with the exception of [(salph)Al(THF)2][Co(CO)4], as catalyst, wherein the lactones are mixtures of S- and R-lactones having an excess of one enantionmer.