A microwave-assisted synthesis of julolidine-9-carboxamide derivatives and their conversion to chalcogenoxanthones via directed metalation.
9-formyljulolidine was oxidized via a microwave-assisted Willgerodt-Kindler reaction to the N-piperidine or N-morpholine julolidine-9-thioamide. 9-formyl-1,1,7,7-tetramethyljulolidine gave the corresponding N-piperidine tetramethyljulolidine-9-thioamide. The thioamides were converted to the corresponding carboxamides with trifluoroacetic anhydride. The amide group directed ortho-metalation in the julolidine system, but not in the tetramethyljulolidine system. The resulting anion was captured by dichalcogenide electrophiles. The resulting products were converted to chalcogenoxanthones with phosphorus oxychloride and triethylamine (POCl3/Et3N).
Holt
Jason J
JJ
Department of Chemistry, The State University of New York at Buffalo, Buffalo, New York 14260-3000, USA.
Calitree
Brandon D
BD
Vincek
Josiah
J
Gannon
Michael K
MK
Detty
Michael R
MR