2,3-dimethyl butadiene, telomerization

Butadiene telomerizes with chiral cyclohexanone-derived enamines under substrate control with (5)-2-(methoxymethyl)pyrrolidine (SMP) or its a,a-dimethyl analog as chiral auxiliary12. After removal of the auxiliary by hydrolysis, 2-[( )-2,7-octadienyl]cyclohexanone (6) is obtained in 57 % yield with 72 % ee (R = H) or in 60 % yield with 92 % ee (R = CH3). Cyclopen-tanones, cycloheptanones and cyclooctanones can be similarly converted. 

The second example is the telomerization of phthalic acid with butadiene yielding bis(octadienyl) phthalates, which can then be hydrogenated to the bisoctyl phthalates which may be used as plastic softeners. The catalyst is formed from palladium bis(acetylacetonate) and tris(p-methoxyphenyl)phosphite in the polar solvent dimethyl sulfoxide. Once again the extraction can be carried out with isooctane [58, 59]. 

Dimethylbutadiene is a symmetrical molecule like butadiene and, therefore, only three isomeric telomers can be expected. However, this diene is a very inactive one and only in one case has telomerization been reported. The reaction of 2,3-dimethyl-l,3-butadiene with ethylacetoacet-ate in the presence of a [PdCl2(PPh3)2]/NaOPh catalyst results in the formation of ethyl-2-acetyl-2,3,6,7-tetramethyl-2,7-decadienoate (31) with a yield of 7% [37, 38]. 

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