Microwave-assisted synthesis of medium-sized heterocycles

Abstract

The development of new strategies for synthesis of medium-sized heterocycles has remained a highly attractive but challenging proposition. In the last few years, the application of microwave irradiation has greatly facilitated the construction of such heterocyclic ring systems through a myriad of different synthetic approaches. This feature article illustrates the progress made in the microwave-assisted synthesis of medium-sized heterocycles with an emphasis on examples describing the use of a dedicated microwave synthesizer.

Montmorillonite Clay-Promoted, Solvent-Free Cross-Aldol Condensations under Focused Microwave Irradiation

“…In this context, a particularly important area is the development of synthetic processes in the absence of solvents [19][20][21][22]. Microwave-assisted organic synthesis (MAOS) has emerged as an efficient and powerful tool in this area [23][24][25][26][27][28] and often leads to simple protocols, short processing times, increased product yields, energy savings [29] and lower costs, thereby enabling environmentally friendly processes [30]. On the other hand, methods based on the use of heterogeneous catalysts are widely used in industrial fine and pharmaceutical chemistry, and play an important role in the current bid for the development of green synthetic processes.…”

Review of Microwave-Assisted Synthesis of Benzo-Fused Six-MemberedN,N-Heterocycles

“…This clearly demonstrates the powerful combination of MW and multi-component synthesis. [113,114] This methodology was successfully extended to a one-pot total synthesis of complex heterocyclic systems such as pyrazino [2,1-b] Boc protecting group and diketopiperazinelike cyclization to afford the target heterocycle. [115] …”

Role of Microwaves in the Synthesis of Fused Five-Membered Heterocycles with Three N-Heteroatoms

“…When the above reaction was carried out using sodium ethoxide as catalyst either by conventional heating or MW, the two 1,2,4-triazolo [1,3,4] co-workers [77] disclosed a microwave promoted synthesis of thiadiazepines possessing fused benzopyranotriazole rings via a tandem Michael addition-condensation reaction between 3-arylidene flavanones and 4-amino-5-alkyl 3-mercaptotriazole using basic alumina as solid support at 145 o C for 3 min (Scheme 36). [78] A novel and efficient method for the synthesis of substituted thiazepines and diazepines has been developed. A simple one pot reaction of chalcones with 1-amino-2-mercapto-5- 39).…”