In this work, a summary of PPSE composition and applications, specially those related to synthesis of heterocycles is presented, and comparison with related reagents such as polyphosphoric acid (PPA) and polyphosphoric acid ethyl esther (PPE) is made. Its usefulness in the synthesis of heterocyclic seven membered amidines, namely 1,2-diaryl- 1H-4,5,6,7-tetrahydro-1,3-diazepines, is also investigated. Results are compared with those obtained with typically PPE cyclizations.