Microwave pericyclic reactions

This chapter has taken the reader through a number of microwave-assisted methodologies to prepare and further functionalize 2-pyridone containing heterocycles. A survey of inter-, intramolecular-, and pericyclic reactions together with electrophilic, nucleophilic and transition metal mediated methodologies has been exemplified. Still, a number of methods remain to be advanced into microwave-assisted organic synthesis and we hope that the smorgasbord of reactions presented in this chapter will inspire to more successful research in this area. 

The best solvent from an ecological point of view is without doubt no solvent. There are many great reactions that can already be carried out in the absence of a solvent, for example numerous industrially important gas-phase reactions and many polymerizations. Diels-Alder and other pericyclic reactions are also often carried out without solvents. Reports on solvent-free reactions have, however, become increasingly frequent and specialized over the past few years. Areas of growth include reactions between solids [5], between gases and solids [6], and on supported inorganic materials [7], which in many cases are accelerated or even made possible through microwave irradiation [8]. 

Choshi, T., Kumemura, T., Nobuhiro, J., and Hibino, S. 2008. Novel synthesis of the 2-azaanthraquinone alkaloid, scorpinone, based on two microwave-assisted pericyclic reactions. Tetrahedron Letters, 49 3725-28. 

Soares, M.I.L., Teresa M.V.D., and Melo, P. 2008. Microwave-assisted generation and reactivity of aza- and diazafulveniummethides Heterocycles via pericyclic reactions. Tetrahedron Letters, 49 4889-93. 

In a series of publications over the past few years, the group of Barriault has reported on microwave-assisted tandem oxy-Cope/Claisen/ene and closely related reactions [175-178], These pericyclic transformations typically proceed in a highly stereoselective fashion and can be exploited for the synthesis of complex natural products possessing decalin skeletons, such as the abietane diterpene wiedamannic... 

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