H 44 a And bis-alkylated adduct 4e'(24%), where R2= CH3. a phenyl group is present on the 5-alkyl moiety to direct alkylationadjacent to it. The origin for the regioselectivity in the alkylation of 1, 5-and 2, 5-substituted tetrazolee is not obvious. A number of factors such aa pK, of substrate, kinetic acidity of protons, metalating agent, and solvent polarity affect a metalation rea~ tion.~
