Convergent synthesis of cis-α,β-epoxy-carboxylic acids from 1-halo-2-trimethylsilyloxy-3-aza-4-phenyl-1,3-butadiene

Reaction of a wide variety of aldehydes with the easily prepared 2-azadienes, in the presence of BF3 etherate, furnishes the corresponding hetero Diels–Alder adducts which have been converted, mainly, to cis epoxides via N-Boc protection followed by one-pot two-step ring opening and nucleophilic displacement of the halogen atom, resulting in final formation of an oxirane ring.