Synthesis of optically active 3-amino-2,3-dihydrobenzopyran-4-ones by ringtransformation of aziridinecarboxamides

Weinreb amides 1 of aziridinecarboxylic acids react with o-lithiated O-meth oxymethylphenols 2 to 2-benzoylaziridines 3 which, after O-deprotection, un dergo ring transformation by attack of the phenolic hydroxy group at 3-posi tion of the aziridine ring affording optically active 3-aminodihydrobenzopy ran-4-ones 5 under acidic conditions. Alternatively, 5-membered benzofuran- 3-ones 6 and 7 can be obtained under basic conditions.