Eine einfache synthese von 1,3-dihydro-1,3-diborapentafulven-derivaten: A convenient synthesis of 1,3-dihydro-1,3-diborapentafulvene derivatives

Reaction of 3,3-dimethyl-1-butynyllithium with boron trichloride followed by hydroboration with HBCl2 leads to 1,1-bis(dichloroboryl)-3,3-dimethylbutene (4a). Halogen exchange with boron triiodide yields the corresponding tetraiodide 4b, which undergoes a redox reaction with 3-hexyne to give the 1,3-dihydro-1,3-diborapentafulvene 3b. Its 1,3-dimethyl derivative 3c is less stable and rearranges to nido-C4B2 carboranes as well as to polymeric products. Hydroboration of 3c with HBEt2 results in the formation of the nido-C3B3 carborane 6c. The reaction of 3c with Mo(CO)6 yields the 1,3-diborapentafulvene complex 7c.