Butadiene, hydrophosphination

The hydrophosphination of 1,3-butadiene with PH3 catalyzed by Cp2EuH should proceed predominantly via a 1,4-addition and to a lesser extend through a 1,2-addition pathway based on a computational study [189]. The reaction of isoprene with diphenylphosphine indeed forms both regioisomers (49) [186], Isolated double bonds are also reactive, as styrene derivatives are almost as reactive as alkynes (50) however, simple unactivated alkenes, such as 1-decene, are unreactive even at elevated temperatures [186]. 

In related Ni-catalyzed hydrophosphination of propargyl alcohols, the addition was anti-Markovnikov in ethanol. But, when the catalyst was modified with PPh2(0)(0H), butadiene derivatives 3 and 4 formally derived by dehydration of 5 were obtained 5 was not an intermediate in this process (Scheme 3) [10]. 

More recently, hydrophosphination of butadiene with PH3 catalyzed by the precursor Cp2EuH was investigated computationally [33]. Consistent with the previous experimental work on aUcene hydrophosphination, the active species was proposed to be the phosphido complex Cp2Eu(PH2), and P-C bond formation occurred by insertion into the Eu-P bond. Hydrophosphination of such conjugated dienes by f-element catalysts does not appear to have been studied in the laboratory, but dienes have been prepared from alkyne hydrophosphination, as described below. 

Butadiene derivatives were also prepared by hydrophosphination of enynes catalyzed by Y(HMPA) complexes, which was selective for addition to the triple bond (Scheme 22, HMPA = hexamethylphosphoramide) [36]. 

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