One-step synthesis of pyridines and dihydropyridines in a continuous flow microwave reactor

Figure 1: Microwave flow reactor for the Bohlmann–Rahtz synthesis of pyridine 2b.

 read at
http://www.beilstein-journals.org/bjoc/single/articleFullText.htm?publicId=1860-5397-9-232 

The Bohlmann–Rahtz pyridine synthesis and the Hantzsch dihydropyridine synthesis can be carried out in a microwave flow reactor or using a conductive heating flow platform for the continuous processing of material. 
In the Bohlmann–Rahtz reaction, the use of a Brønsted acid catalyst allows Michael addition and cyclodehydration to be carried out in a single step without isolation of intermediates to give the corresponding trisubstituted pyridine as a single regioisomer in good yield. 
Furthermore, 3-substituted propargyl aldehydes undergo Hantzsch dihydropyridine synthesis in preference to Bohlmann–Rahtz reaction in a very high yielding process that is readily transferred to continuous flow processing.

Mark C. Bagley¹, Vincenzo Fusillo², Robert L. Jenkins², M. Caterina Lubinu² andChristopher Mason³

¹Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton, East Sussex, BN1 9QJ, UK
²School of Chemistry, Main Building, Cardiff University, Park Place, Cardiff, CF10 3AT, UK
³CEM Microwave Technology Ltd, 2 Middle Slade, Buckingham, MK18 1WA, UK

This article is part of the Thematic Series "Chemistry in flow systems III".

Guest Editor: A. Kirschning

Beilstein J. Org. Chem. 2013, 9, 1957–1968.

Microwave-assisted synthesis of N-heterocycles in medicinal chemistry

Med. Chem. Commun., 2013, 4,1323-1343
DOI: 10.1039/C3MD00152K, Review Article

Davide Garella, Emily Borretto, Antonella Di Stilo, Katia Martina, Giancarlo Cravotto, Pedro Cintas
Microwave-assisted synthesis of heterocycle libraries has given an impressive contribution to drug discovery and development.http://pubs.rsc.org/en/Content/ArticleLanding/2013/MD/C3MD00152K?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FMD+%28RSC+-+Med.+Chem.+Commun.+latest+articles%29#!divAbstract

 

Microwave-assisted synthesis of N-heterocycles in medicinal chemistry

 

 

 The syntheses of almost all N-heterocycles have now been successfully performed under microwave irradiation and have provided significant improvements in the reaction time and efficiency. The peculiar properties of dielectric heating give it the ability to strongly promote cyclocondensation, cycloaddition and selective N-heterocycle functionalisation and it has, therefore, very much caught the attention of the medicinal chemistry community. In this work, we present an overview of recent literature and technical advances in this research field with the aim of providing insight into the applications of microwave-assisted synthesis in the preparation of the main drug categories that contain N-heterocycle scaffolds.