Synthesis of dibenzothiazines dioxide polysubstituted via Transition Metal Catalyzed [2+2+2] Cycloaddition Reactions

Polysubstituted dibenzothiazines as well as benzothiazines and
sulfonamides constitute a group of compounds with interesting
biological activities. Only few works report the synthesis of
polysubstituted dibenzothiazines dioxide [1]. We propose here a new
ring-formation approach that allows polyfunctional dibenzothiazine
core via transition metal-catalyzed [2+2+2] cycloaddition reactions of
o-alkynyl-N-alkynyl-benzene sulfonamide and propargylic alcohol to
give interesting new heterocycles. The synthesis of ynamide will be
the key step of this strategy as an important precursor of these
compounds.