Microwave-assisted solvent-free intramolecular 1,3-dipolar cycloaddition reactions leading to hexahydrochromeno[4,3-b]pyrroles: scope and limitations

We report the microwave-assisted solvent-free synthesis of hexahydrochromeno[4,3-b]pyrroles. Intramolecular 1,3-dipolar cycloadditions proceed under these conditions within 15-40 min in 16-84% yields. An influence of the microwave irradiation upon various [3+2] cycloaddition reaction intermediates was studied. Additionally, a scope and limitations of these reactions including an influence of the dipolarophile geometry upon the cycloaddition selectivity and steric demands of the dipole upon its reactivity were also disclosed. These observations led us to postulate a preferable transition state of the reaction. Finally, an influence of the microwave irradiation to the isomerization of activated olefins was also described. (c) 2006 Elsevier Ltd. All rights reserved

Microwave-assisted solvent-free synthesis of hexahydrochromeno-[4,3-b]pyrroles

We report the microwave-assisted solvent-free synthesis of hexahydrochromeno[4,3-b]pyrroles. Intramolecular 1,3-dipolar cycloadditions proceed under these conditions within 15 min in 80% yields. Moreover, we have observed pronounced steric requirements of alkyl substituents toward the 1,3-dipolar cycloadditions. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004

A solvent-free method for substituted imidazolidin- 4-ones synthesis

A new method of the solvent-free synthesis of substituted imidazolidin-4-ones is described. The method is developed for microwave-assisted solvent-free conditions and compared with classical thermally initiated solvent-free conditions. In both cases the reaction proceeds with good yields. However, the reaction under microwave conditions is accelerated six-times. Thermal effect of the microwaves is observed