Trifunctionalized Allenes. Part IV. Cyclization Reactions of 4-Phosphorylated 5-Hydroxyhexa-2,3-dienoates

This manuscript focuses on the reactions of 4-phosphorylated 5-hydroxyhexa-2,3-dienoates with protected or unprotected hydroxy groups involving 5-endo-trig cyclizations. Reactions with electrophiles result in mixtures of the 2,5-dihydro-1,2-oxaphosphole-5-carboxylates and the 5-phosphorylfuran- 2(5H)-ones by competitive electrophilic cyclization due to the neighboring phosphonate (phosphine oxide) and the carboxylate groups participation. 4-Phosphorylated 5-hydroxyhexa-2,3-dienoates were smoothly transformed into the corresponding 4-phosphoryl-2,5-dihydrofuran-2-carboxylates by using 5 mol % of a silver salt as a catalyst in the 5-endo-trig cycloisomerization reaction.