A convenient approach is presented for the preparation of substituted
amidines through the fusion of N-Pmc-substituted thioamides with
amines, facilitated by a variety of thiophilic reagents. Assorted
thiophiles were evaluated for their effectiveness as condensation
reagents between the two partners, with the Mukaiyama reagent emerging
as the optimal candidate for this process. The scope and limitations
of this method were explored, revealing interesting synthetic challenges
and constraints. Many of these limitations were overcome through
the application of alternative reaction pathways in the construction
of troublesome products. Treatment of the resultant Pmc-amidines
with trifluoroacetic acid and trimethylsilyl trifluoromethanesulfonate
cleanly afforded the deprotected substituted amidines.
amidine - thioamide - Mukaiyama reagent - thiophile - N-sulfonyl
