Intramolecular Coupling of Enynes or Alkynes

Within a similar context, nickel(O) complex has been shown to promote cyclization of enynes and isocyanides to form bicydooctenone derivatives in good yields [149]. Phosphine or diimine ligands are required in these reactions [150]. 

It is interesting to note that, in the absence of phosphine ligands, dienes are obtained as the major products [151]. 

The couplings of 1,6- and 1,7-intemal diynes or oxygen-linkage mixed terminal/internal diyne with isocyanides provide useful entries for constructing bicydic cydopentenone skeletons [152]. The cyclizations of symmetric or unsymmetric diynes bearing amine moiety at the tethered chain proceeded with modest to good regioselectivity in acceptable isolated yield [151,153]. 

In the presence of silylhydrides, intramolecular cydizations of 1,7-diynes give stereoselectively the corresponding terminally substituted dienes in good yields [153, 154], 

Interestingly, bisdiene also undergoes a similar cydization - hydrosilation across the two diene units to form trans-l,2-divinylcydopentane derivatives as a mixture of olefin geometrical isomers [151], 

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