Cyclization of 9-Substituted Decanoic Acid Derivatives to 9-Decanolide and 9-Decanelactam

Article abstract of DOI:10.1021/jo00017a027

Several standard and some novel cyclization reactions have been applied to 9-substituted decanoic acids to establish which are the optimum procedures for lactonization and lactamization at 80 deg C under identical high-dilution conditions.The methods of Galli-Mandolini and Kellogg (cyclization of 9-bromodecanoate ion), Gerlach (cyclization of S-2-pyridyl 9-hydroxydecanethioate in the presence of AgClO4), and Yamaguchi (activation of the carboxyl group as a mixed anhydride) in the presence of an excess of DMAP appear to be the most useful for the preparation of the 10-membered lactone, phoracantolide I, under these conditions.Analogously, treatment of S-2-pyridyl 9-azidodecanethionate with Sn(SePh)3(1-) afforded the best yield of the 10-membered lactam.The mixed anhydrides RCOOCOAr (Ar = 2,4,6-trichlorophenyl) are more reactive than thioesters RCOSPy (Py = 2-pyridyl) with benzyl alcohol or benzylamine; it is confirmed that the addition of DMAP activates the reaction of alcohols with mixed anhydrides much more than with pyridyl thioesters, while the addition of Ag(1+) strongly activates RCOSPy in relation to either RCOOCOAr or RCOOSO2Mes.