Recent advances in the cyclization of N-heterocycles: the role of enabling techniques (review)

Abstract

The so-called ''enabling techniques'' can dramatically promote the synthesis of N-heterocycles. Besides facilitating very quick cyclization, these technologies bring with them process intensification, safer protocols, cost reduction, energy savings, and waste minimization. We herein describe a series of efficient N-heterocycle cyclizations carried out under microwave and/or ultrasound irradiation.

Ultrasound‐ and Microwave‐Assisted Preparation of Lead‐Free Palladium Catalysts: Effects on the Kinetics of Diphenylacetylene Semi‐Hydrogenation

“…Non-conventional enabling technologies such as microwaves (MW) and ultrasound (US) foster process intensification, combine safer protocols, and result in cost reduction and energy saving. [23] In comparison to conventional conductive heating, MW irradiation causes volumetric heating via the direct coupling of the electromagnetic field with polar solvents and catalysts in the reaction mixture. As a result, fast selective heating can be attained by irradiating polar materials in an MW field.…”

Use of Ultrasound in the Synthesis of Heterocycles of Medicinal Interest

“…and material science) as previously mentioned. Reactions such as condensation, substitution, oxidation, reduction, addition, protection/deprotection, coupling, photochemical, and polymerization are found to be improved under sonication [2,[41][42][43]. Sonochemistry is a very good alternative technique to synthesize both heterocycles and fused heterocycles with short reaction times, high yields, and mild conditions [2,39,40].…”

Ultrasonically improved semi-hydrogenation of alkynes to (Z-)alkenes over novel lead-free Pd/Boehmite catalysts

“…The beneficial effects of ultrasound (US) are well documented in the literature [2,27]. This non-conventional enabling technology furthers process intensification and combines safer protocols, cost reduction and energy savings [28]. Ultrasound has been applied to the activation of heterogeneous catalytic hydrogenation since the early 1980s [29][30][31].…”