Competition between Peroxy Acid Oxygens as Hydrogen Bond Acceptors in B3LYP Transition Structures for Epoxidations of Allylic Alcohols with Peroxyformic Acid

The transition structures (TSs) for the epoxidation of 2-propen-1-ol and 2-cyclobuten-1-ol with peroxyformic acid have been located with the B3LYP method using three basis sets (i.e., 6-31G*, 6-311G**, and 6-311+G**). Syn attacks on these alcohols by peroxy acid lead to syn TSs in which hydrogen bonding is operative. The allylic OH group always acts as hydrogen-bond donor while either the carbonyl oxygen or the peroxo oxygens of the peroxy acid can play the role of hydrogenbond acceptors. The Sharpless qualitative TS model for peroxy acid epoxidation of allyic alcohols is discussed in the light of computational data.