Laser flash photolysis of chloro(pyridyl)carbene and derivatives in solution and heterogeneous media

ORGN 578

Reinaldo Moya-Barrios, rbarrios@dal.ca, Frances L. Cozens, frances.cozens@dal.ca, and Norman P. Schepp. Department of Chemistry, Dalhousie University, Halifax, NS B3H 4J3, Canada
Laser flash photolysis of 3-chloro-3-(4-pyridyl)diazirine (PyClCN2) in hydrocarbon solution generated the chloro(pyridyl)carbene (PyClC:), a highly reactive species that could not be directly observed with our nanosecond laser system. Instead, PyClC: was indirectly detected through the formation of a pyridine-like ylide generated via reaction with the diazirine precursor. Saturation of the ylide signal with excess of PyClCN2 allowed the Stern-Volmer quenching with different alkenes. The quenching data revealed the strongly electrophilic character of this species, in contrast with the well-studied ambiphilicity of arylhalocarbenes. In addition, the steric and electronic influence of substituents on the stability of halo(pyridyl)carbenes was studied. Lastly, the effect of zeolite encapsulation on the decay mechanism of halo(pyridyl)carbenes was also compared to the behavior of the carbene in hydrocarbon solution.