Synthesis of Polysubstituted Pyrroles via Dihydro-1,2-oxazines

Significance

A method for the synthesis of polysubstituted pyrroles via Diels-Alder adducts derived from the reaction of dienes with tert-butyl N-hydroxycarbamate is reported. The reaction of the dienes with tert-butyl N-oxocarbamate, derived by in situ oxidation from N-Boc-hydroxyl­amine leads to oxazines in good to excellent yields and regioselectivities from 55:45 to 2:98 depending on the diene. Reductive ring opening using NaBH₄ in the presence of Mo(CO)₆ gave the corresponding amino alcohols which, under MnO₂ or Dess-Martin periodinane oxidative conditions and subsequent cyclization, led to the final pyrrole derivatives in excellent yields.