Enantiopure 1,4-Benzoxazines via 1,2-Cyclic Sulfamidates. Synthesis of Levofloxacin.

1,2-Cyclic sulfamidates undergo efficient and regiospecific nucleophilic cleavage with 2-bromophenols (and related anilines and thiophenols), followed by Pd(0)-mediated amination to provide an entry to substituted and enantiomerically pure 1,4-benzoxazines (and quinoxalines and 1,4-benzothiazines). This chemistry provides a short and efficient entry to (3S)-3-methyl-1,4-benzoxazine 19, a late stage intermediate in the synthesis of levofloxacin.