Synthesis of New Polycyclic γ- and δ-Lactones upon Activation of, and Nucleophilic Additions to, Diazines: Influence of the Activating Agents

The reaction of bis(trimethylsilyl)ketene acetals 2 with N-heterocycles containing either one or two nitrogen atoms in the presence of triflic anhydride has been examined and the structures of the resulting products compared with those obtained by using methyl chloroformate as the activating agent. Whereas pyridine, pyrazine, quinoxaline and pyrimidine led to the same type of fused δ- or γ-lactones 4, 6, 8, 10 and 11 as with methyl chloroformate, the behaviour of pyridazine appeared to be peculiar. In the presence of methyl chloroformate, this heterocycle led to δ-lactones 16 via stable dihydropyridazines, with triflic anhydride, the direct formation of γ-lactones 20 was observed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)