METALLOMETALLATION OF ALLENES - AN EXPLORATORY-STUDY

Reaction of either n-Bu3SnCu(CN)Li (8) or (n-Bu3Sn)2Cu(CN)Li2 (9) with 1,2-undecadiene gave 71-92% of a (Z/E) mixture of 1-tri-n-butylstannyl-2-undecene (27) accompanied by 8-32% of a mixture of (E)-2-tri-n-butylstannyl-2-undecene (28) and 2-tri-n-butylstannyl-1-undecene (29). When the above reactions were warmed to 0-degrees-C, 28 and 29 were the major products. The mixed cuprates, 10-14, gave the mixtures rich in vinylstannanes, 28 and 29, along with 27. Addition of Sn-Al reagents, 15 and 16, or Sn-B reagents, 18 and 19, to 1,2-undecadiene in the presence of 5 mol% of CuCN or CoCl2.(PPh3)2 provided mixtures rich in vinylstannanes, 28 and 29. However, with 1 equiv. of CuCN, mixtures rich in allylstannanes 27 were obtained. Reaction of 5-hydroxy- 1,2-pentadiene with the Sn-Al reagents, 15 and 16, gave 53-61% of a single 5-hydroxy-2-tri-n-butylstannyl-1-pentene (32) in the presence of 5 mol% of CoCl2.(PPh3)2. The stannylcopper adducts generated in the reaction of 1,2-undecadiene and 8 or 9 were treated with iodomethane to give 55-78% of a (Z/E: 67/33) mixture of 1-tri-n-butylstannyl-2-methyl-2-undecene (33). Addition of mixed silylcuprates, 21, 22, and 23, to 1,2-undecadiene gave mixtures rich in (E)-2-dimethylphenylsilyl-2-undecene (35) and 2-dimethylphenylsilyl-1-undecene (36). A rationale for the putative adducts' formation is also presented.