Triazole phosphonates. Electrophilic substitution of 1-substituted-1H-1,2,4-triazoles via lithiated triazole intermediates

The metalation chemistry of several 1-substituted-1H-1,2,4-triazoles has been investigated. When various alkyl groups were incorporated in the 1-position, lithiation proceeded exclusively at C-5. The 1-trityl-, 1-methyl-, and 1-benzyl-5-lithio-1,2,4-triazoles were stable at ?78° and reacted cleanly with a variety of electrophiles. The 1-benzyl and 1-methyl derivatives were synthetically more versatile and could be successfully utilized to prepare several examples of the previously unknown 1,2,4-triazol-5-yl phosphonates.