Development of Organic Synthetic Reaction Utilizing Charge Reversal of pi-Allylpalladium Complex

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I have found that palladium-catalyzed carbonyl allylation by allylic alcohols with SnCl_2 smoothly proceeds in aqueous medium under air. Allylic alcohols, preparing pi-allylpalladium complexes, function as synthons of allylic carbanions. In other words, this implies the apparent charge reversal of electrophilic pi-allylpalladium complexes. The carbonyl allylation by allylic alcohols can achieve high chemo-, regio-, and diastereoselection by the choice of solvent. Here I report about the full scope, limitations, and mechanism of this new process : 1. ^1H, ^<13>C, and ^<119>Sn NMR investigation has elucidated that the actual allylating agent in the carbonyl allylation by allyl alcohol in dry medium is allyltrichlorotin, which is prepared via (1) oxidative addition of allyl alcohol to Pd (O) complex with SnCl_2, (2) insertion of SnCl_2 to pi-allylpalladium complex, followed by (3) reductive elimination of pi-allylpalladium trichlorostannate. 2. This carbonyl allylation in polar solvent has been applied to chelation-controlled diastereoselection ; (1) the chelation of omega-hydroxy carbonyl compound to Sn (IV) in allylic tin, (2) the chelation of intramolecular ethoxycarbonyl group to Sn (IV) in 1-substituted 2-ethoxycarbonyl-2-propenyltin, and (3) the chelation of intramolecular hydroxy group to Sn (IV) in 4-substituted 4-hydroxy-2-butenyltin. 3. Intramolecular carbonyl allylation has been carried out using (1) 4-hydroxymethyl-4-pentenals prepared by Claisen rearrangement of 2-hydroxymethylallyl vinyl ethers and (2) 7-hydroxy-5-heptenals prepared by oxy-Cope rearrangement of 3-hydroxy-4-hydroxymethyl-1, 5-hexadienes. 4. Ultrasound-promoted carbonyl allylation by 3-substituted allylic alcohol in nonpolar solvent has caused inversed regiocontrol to the carbonyl allylation in polar solvent.