In this paper, the results obtained in the synthesis of thioamides and α-ketothioamides by a modification of the Willgerodt–Kindler reaction, under solvent-free and noncatalyst conditions using IR energy as a source of activation, are presented. The use of IR energy in these reactions has been shown to lead to a mixture of thioamide and α-ketothioamide as the main products in most cases, with the latter predominating. The yields of α-ketothioamides from most of these reactions are better than those reported previously. To the best of our knowledge, this is the first time that IR energy has been applied to promote the Willgerodt–Kindler reaction.

A comparative study concerned with the preparation of diversely substituted-1H-benzimidazole under different green activation techniques and conventional methods is reported. Data are collected for infrared, ultrasound, microwave, and simultaneous irradiation with US and IR sources, as this last strategy shows an important improvement. Further, the small library of potentially bioactive benzimidazole 17-76 synthesized was screened as an antifungal and antimicrobial agent. Strong activity against Candida albicans and Staphylococcus aureus was observed. Remarkably, 2-(4-aminophenyl)-5-phenylamino-1H-benzimidazole 63 resulted better than that of reference drugs miconazole with a zone of inhibition up to 42 mm. Likewise, 2-(2-aminophenyl)-1H-benzimidazole 21 showed substantial antimicrobial activity against MRSA strain. When assayed by the microdilution method, this azaheterocyclic compound presented a minimum inhibitory concentration (MIC) ≥ 16.4 μg/100 mL and a bacterial percentage reduction of 96%. a Reactions were obtained by exposing the reactants to 2-minute cycling pulse sequences of US (with 5-min intermittent cooling). b Reactions were obtained by exposing the reaction to 1-minute cycling pulse sequences of US combined with IR irradiation (with 5-min intermittent cooling). c Reactions were subjected to one pulse sequences by the required time. d Reactions were submitted to react in presence of 1.8 mol% (1 equiv) of radical inhibitor 1,4-benzoquinone (Q). e Reactions were summited to react by the required time. F I G U R E 1 (A) Comparison of two feasible pathways of reaction (ionic-radical) induced by MW and SIUI and (B) overview ofcavitation bubble dynamics, their physical and chemical effects. In cavitation, bubbles collapse produce transient hot-spots that reach 5000 K and 1000 atm in a short span of time capable to generate a heating/cooling rate of more than 1000 K/s. [17] Thereby, hot-spot drive highenergy chemical reactions predominantly associated with the SET process. SET, single electron transfer [Color figure can be viewed at wileyonlinelibrary.com] PENIERES-CARRILLO ET AL. 438 a Reactions were obtained by exposing the reactants to 2-minute cycling pulse sequences of US (with 5-min intermittent cooling). b Reactions were obtained by exposing the reaction to 1-minute cycling pulse sequences of US combined with IR irradiation (with 5-min intermittent cooling). c Reactions were subjected to one pulse sequences by the required time. d Reactions were summited to react by the required time.Note. The values of inhibition are expressed in mm.; compounds 19, 23, 25, 29, 36, 42, 43, 46-57, 59, 62, 64, and 68-71 shown none activity.

The efficiency of conventional heating energy source compared with Infrared (IR), Ultrasound (US), Microwave and the simultaneous combination US-IR eco-friendly approaches for preparation of new N-(5-R 1 -amino-2-nitrophenyl)acetamides and 5-R 1 -amino-2-nitroaniline by Nucleophilic Aromatic Substitution (S N Ar) via addition-elimination reactions on the halogens F, Cl, Br, I, employing amines as nucleophiles were explored. Moreover, phenyldiazenyl derivatives in good yields by an oxidative one-pot S N Ar-based amination reaction from an unusual oxidation of 2phenylhydrazinyl derivatives in DMSO was prepared. ARTICLE HISTORY