Introduction
Benzodiazepines are a family of compounds with recognised central nervous system depressant action, widely used as anxiolytics, anticonvulsants and sedatives^1-3. In this context, N'-substituted 2-aminoacetanilides are key synthetic precursors for obtaining new 1,4-benzodiazepin-2-ones with potential biological activity.

This study summarised and conducted a structural analysis of acetanilides, characterised by the presence of a semi-rigid amide bond that enables E/Z isomerism. Structural analysis is essential, as the conformation adopted can determine the obtaining of compounds with potential biological activity ⁴.

Methods
N'-substituted 2-aminoacetanilides were synthesised using a two-step procedure: in the first step, anilines were acylated with chloroacetyl chloride; in the second step, these intermediates underwent a nucleophilic substitution reaction with methylamine.

The products obtained were purified by recrystallisation and characterised by determining their melting point and using spectroscopic techniques. Subsequently, theoretical calculations were performed using Gaussian 03 software. The structures were optimised using the DFT method (B3LYP/6-311G[d,p] in vacuum) and then their isotropic shielding tensors were obtained using the GIAO-B3LYP/6-31+G(d,p) method in chloroform. The isotropic shielding values of 1H were converted into chemical shifts by subtracting the analogous values of TMS⁵.

Results and Conclusions

The synthesised compounds were obtained with good yields and high reproducibility. The ¹H NMR spectra indicated the presence of a single rotamer, whose identity was confirmed by theoretical calculations. These preliminary results support the synthetic and analytical approach, providing a solid basis for the rational design of new benzodiazepines with potential pharmacological applications.