Mechanistic studies on Pd-catalyzed telomerization and co-cyclization of butadiene: Amphiphilicity of bis-pi-allylpalladium intermediate in the presence of phosphine ligand

Pd-catalyzed reactions of butadiene, which proceed through a bis-pi -allylp alladium intermediate, (eta (3), eta (3)-C8H12)Pd (2), were performed in th e presence of both a pronucleophile (aceto- or cyanoacetate) and an electro phile (benzaldehyde). Methyl aceto- or cyanoacetate and benzaldehyde reacte d independently with 2 to give telomers 8 and the divinyl-substituted pyran es 9, respectively. In the case of methyl cyanoacetate, the co-cyclization of 2 with 2-cyano-3-phenylpropenoate (11) formed in situ also took place to afford the cyclohexane derivative 10. Namely, three kinds of amphiphilic a dditions of the C-8-chain of 2 occurred to Hdelta+-Nu(delta-), Cdelta+=Cdel ta-, and Cdelta+=Odelta- simultaneously in a one-pot reaction. The Pd-catal yzed reaction of allyl chloride, allyltributylstannane, methyl cyanoacetate , and benzaldehyde. was undertaken under neutral conditions, expecting the amphiphilic reactions by the intermediacy of (eta (3)-C3H5)(2)Pd (6) formed in situ. Allylation of both benzaldehyde and methyl cyanoacetate took plac e. Competitively amphiphilic bis-allylation of the polar double bond of 11 also occurred to form the 1,7-octadiene derivative 18. The mechanisms of bo th reactions can be explainable in terms of the amphiphilicity of the inter mediates (2 and 6) in the presence of a phosphine ligand.