Reluctance of 4-Chloro-5-metalla-1,3,2-diazaborolines To Undergo Metal Halide beta-Elimination: An Opportunity for C-Functionalization of 1,3,2-Diazaborolines

N,N'-Bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene reacts with dichlorophenylborane, affording the N,N'-bis(2,6-diisopropylphenyl)-2-phenyl-4-chloro-1,3,2-diazaboroline in a one-step process. The addition of lithium diisopropylamide gives rise to the 4-chloro-5-lithio-1,3,2-diazaboroline derivative, which cleanly undergoes a transmetalation reaction with TiCl4 center dot 2THF. Both the lithium and titanium complexes are stable with respect to metal chloride elimination and have been characterized by multinuclear NMR spectroscopy and by single-crystal X-ray diffraction studies. These findings open an avenue for the C-functionalization of 1,3,2-diazaborolines.