SYNTHESIS OF HALOMETHYL AND OTHER BIPYRIDINE DERIVATIVES BY REACTION OF 4,4'-BIS[(TRIMETHYLSILYL)METHYL]-2,2'-BIPYRIDINE WITH ELECTROPHILESIN THE PRESENCE OF FLUORIDE-ION

Bipyridine (bpy) ligands figure prominently in many areas of chemistry . Common precursors to many derivatives are the halomethyl-substituted analogues. This report describes a new, high yield route to these val uable compounds via a trimethylsilyl (TMS) intermediate. 4,4'-Dimethyl -2,2'-bpy was reacted with lithium diisopropylamide, and the dianion t hus formed was trapped with TMSCl to generate 4,4'-bis[(trimethylsilyl )methyl]-2,2'-bp (1). The TMS group was removed using dry F- sources ( TBAF/SiO2 in THF or CsF in DMF) in the presence of BrF2CCF2Br or Cl3CC Cl3 to pro duce the bromide 2 or chloride 3 analogues of 4,4'-bis(halo methyl)-2,2'-bipyridine, respectively. The CsF/DMF methodology extends to other electrophiles, including benzaldehyde to give 4,4'-bis(2-hyd roxy-2-phenethyl)-2,2'-bpy, 6, as well as to alkyl halides. Benzyl Br, dodecyl Br, and alpha-chloroacetonitrile gave mixtures of di- and mon oalkylated products along with the diprotonated product, 4,4'-dimethyl -2,2'-bpy.