This work focuses on the development of a new synthesis route by reducing the number of reactants for the synthesis of phosphate-based materials. This synthesis strategy was developed by using alkylphosphoramide which can play both the role of precursor of the structure-directing agent (SDA) and the phosphorus source. In this work we present the case of hexamethylphosphoramide, tris(N,N-tetramethylene)phosphoric acid triamide, tris(diethylamino)phosphine and trimorpholinophosphine oxide. 1H and 31P liquid NMR spectroscopy was used to fully characterize the decomposition of the alkylphosphoramide. It has been found that the heating temperature, the presence of an acid and ethylene glycol play a crucial role on the alkylphosphoramide decomposition. The synthesis results obtained for the gallophosphate and aluminophosphate systems are reported. The in situ generation of the SDA and the phosphorus source allowed preparing known crystallized gallophosphates and aluminophosphates. For the fluorogallophosphate ULM-3, the 1H liquid NMR spectrum shows clearly the presence of dimethylamine and ammonium cations as structure-directing agents. A new aluminophosphate has been obtained. Finally, a decomposition mechanism of the alkylphosphoramides was proposed for the different reaction media under study.