Development of Efficient Functionalization Using Organozirconium and Organoselenium Compouds

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Organozirconium compounds are useful for organic synthesis by utilizing the reactivity 01 zirconium-carbon bond with a variety of electrophilic reagents to give desired organic molecules. On the other hand, organoselenium chemistry became a very powerful tool in organic synthesis in recent times. Of perticular importance is the phenylseleno (PhSe) group owing to its easily handled nature. One of the most common and useful transformations of this group is its oxidative removal leading to olefins or allylic alcohols via selenoxide elimination or [2,3] sigmatropic rearrangement, respectively.Zirconacyclopentenes (1) are easily prepared by coupling reaction of a low valent zirconocene with alkynes. The reaction of 1 with PhSeBr followed by proton quenching gave vinylselenides in good yields regioselectively. These compounds were oxidized to give the corresponding allene derivatives in good yields via selenoxide elimination. On the other hand, hydrozirconation of terminal alkynes having a phenylseleno group at alpha or beta position with Cp2ZrHCI (Schwartz reagent) gave the corresponding terminal vinylzirconocene derivatives regio- and stereoselectively. These vinylzirconium compounds reacted with a higher order cuprate to generate vinylcuprate intermediates via Zr-Cu transmetalation, which in the presence of electrophiles such as enones, epoxides, or benzyl bromide underwent the coupling reaction with them effectively to afford the adducts in good yields. The adducts with a phenylseleno group were oxidized with excess amounts of H202 to yield the desired products having allylic alcohol or F-shaped conjugated diene moiety in high yields via [2,3] sigmatropic rearrangement or selenoxide syn elimination, respectively.