Room Temperature Ring-Opening Metathesis of Pyridines by a Transient Ti⋮C Linkage

The transient titanium alkylidyne complex (PNP)TiCtBu (PNP = N[2-P(CHMe2)2-4-methylphenyl]2-), prepared from alpha-hydrogen abstraction of the corresponding alkylidene-alkyl species (PNP)Ti=CHtBu(CH2tBu), can readily cleave the C-N bond of N-heterocycles such as pyridine and 4-picoline at room temperature to afford azametallabicyclic systems. Experimental and theoretical studies strongly favor a ring-opening metathesis pathway where [2 + 2] cycloaddition of pyridine across the TiC linkage ultimately leads to C-N bond rupture.