Methods for preparing penams

A method of forming a compound of formula (II) in which a compound of formula (I) is reacted with less than a molar equivalent of a compound of formula (V): wherein R 1 in each occurrence is independently selected from H, halogen, amino, C 1-5 alkyl, C 2-5 alkenyl and C 2-5 alkynyl; R 2 in each occurrence is independently selected from H, halogen, amino, C 1-5 alkyl, C 2-5 alkenyl and C 2-5 alkynyl; R 3 in each occurrence is independently selected from the group consisting of C 1-5 alkoxy and C 1-10 hydrocarbyl; and R 5 is C 1-5 alkyl.