Palladium-Catalyzed Reactions of Butadiene and Isoprene

J. Tsuji, Adv. Organomet. Chem., 1979, 17, 141-193. Palladium-Catalyzed Reactions of Butadiene and Isoprene. 

Palladium-catalyzed addition of phenylsulfinic acid to butadiene and isoprene gave mainly 1,2-addition products. From butadiene, a 4 1 ratio of 1,2- to 1,4-addition product was obtained in high yield [Eq.(ll)] [27]. It was later shown that the 1,2-addition product is the kinetic product and that prolonged reaction time increased the amount of 1,4-addition product [27b]. 

Simple 1,3-dienes such as 1,3-butadiene, isoprene, and related compounds undergo efficient metal-catalyzed oligomerization. Under palladium catalysis, diene dimerization is the most common oligomerization reaction observed. Four modes of dimerization have been reported (Scheme 1) (i) [2 + 2] cycloaddition to afford 1,2-divinylcyclobutane (1) (ii) [4 -I- 2] cycloaddition to afford 4-vinylcyclohexene (2) (iii) [4 + 4] cycloaddition to afford 1,4-cyclooctadiene (3) and (iv) linear dimerization to afford 1,3,7-octatriene (4). 

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