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Activation of Allyl Alcohols as Allyl Cations, Allyl Anions, and Amphiphilic Allylic Species by Palladium



Palladium/Et3B induces allyl alcohols to undergo electrophilic allylation of soft carbonucleophiles (pKa 5–14), alkyl aldehydes at the α-position, and amines, indoles, and tryptophan at the 3-position. The same catalyst, and also Pd/Et2Zn, also effect the generation of allyl anions from allyl alcohols, which react with aromatic and aliphatic aldehydes and imines to furnish homoallyl alcohols and homoallylamines, respectively, in good yields. 2-Methylenepropane-1,3-diol undergoes a sequential amphiphilic activation, generating an allyl cation and an allyl anion, and reacts with aldehydes to furnish 3-methylenecyclopentanols. The amphiphilic activation has been extended to 1,3-bis(alkoxy)-2-methylenepropanes and vinyl epoxides. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)