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- Unsuccessful cyclization conditions included both Lewis acids (SnCl2, AlCl3, BF3, FeCl3, and ZnCl2) and protic acids (H2SO4, TFA, dichloroacetic acid, oxalic acid, HCl, and p-toluene sulfonic acid). Attempted cylcization with P2O5 in the absence of phosphoric acid was also unsuccessful.
- As a reagent for cyclodehydration polyphosphoric acid has found numerous applications in the synthesis of a variety fo aromatic and heteroaromatic systems16,17
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