ZIRCONIUM-MEDIATED REACTIONS OF ALKYLPYRAZINES AND ALKYNES - SYNTHESIS OF HIGHLY SUBSTITUTED ALKYLPYRAZINES

Sequential one-pot addition of alkylpyrazines, alkynes, and a proton source to a solution of Cp2Zr(Me)(THF)+ (1) in CH2Cl2 at room temperature affords (E)-alkenyl-substituted alkylpyrazines 2-10 in excellent yields. The regio- and stereoselectively observed in these reactions is similar to those observed previously for related early transition metal-mediated reactions and is ascribed to steric and Si electronic effects. Conventional synthetic organic manipulation of the alkenylpyrazines provides easy access to a variety of highly substituted alkylpyrazines including tri- and tetrasubstituted alkylpyrazines 13, 17-20, dibromoalkylpyrazine 14, bromoalkylpyrazine 15, and epoxyalkylpyrazine 16.