Nazarov Cyclization Reaction - Classical Nazarov Cyclizations

Classical Nazarov Cyclizations

Though cyclizations following the general template above had been observed prior to Nazarov's involvement, it was his study of the rearrangements of allyl vinyl ketones that marked the first major examination of this process. Nazarov correctly reasoned that the allylic olefin isomerized in situ to form a divinyl ketone before ring closure to the cyclopentenone product. The reaction shown below involves an alkyne oxymercuration reaction to generate the requisite ketone.

Research involving the reaction was relatively quiet in subsequent years, until in the mid-1980s when several syntheses employing the Nazarov cyclization were published. Shown below are key steps in the syntheses of Trichodiene and Nor-Sterepolide, the latter of which is thought to proceed via an unusual alkyne-allene isomerization that generates the divinyl ketone.