Synthesis, Characterization, and Reactions of Mono and Bicyclic Phostones

Improved methods for the synthesis of 5- and 6-membered ring phostones 2 and 1 as well as original preparations of bicyclic phostones 4 (n=1,2) have been successfully executed. The preparation of the 4-membered ring 3 was more elusive, but the observed products indicated its presence as an intermediate which underwent further transformations. Reaction of 1 with 2,2,6,6-tetramethylpiperidide at low temperature, followed by treatment with a variety of alkyl halides gave the expected alkylation products whose cis/trans stereochemistry was dependent on the reaction conditions. Subsequent ring closure of the cis or trans alkylated product 10, gave only the cis fused bicyclic product 4. In fact, other synthetic routes to 4 produced only the cis isomer. The mechanisms and stereochemistry of these various conversions will be discussed.