While B(C6F5)3forms the adducts (CH2)4CO2B(C6F5)31and (CHMeCO2)2B(C6F5)37with δ-valerolactone and lactide, the frustrated Lewis pairs derived from B(C6F5)3and phosphine or N-bases react with lactone to effect ring opening affording zwitterionic species of the form L(CH2)4CO2B(C6F5)3(L = tBu3P 2, Cy3P 3, C5H3Me3N 4, PhNMe25, C5H6Me4NH 6) while reaction with rac-lactide results in ring contraction to give salts [LH][OCCHMeCO2(CMe)OB(C6F5)3] (L = tBu3P 8, Cy3P 9, C5H3Me2N 10, C5H6Me4NH 11). The mechanistic implications of these reactions are discussed. [ABSTRACT FROM AUTHOR]