Improvements in 1,3-dipolar cycloaddition of nitrones to fluorinated dipolarophiles under solvent-free microwave activation

1,3-Dipolar cycloadditions between ethyl trifluoracetoacetate or alpha-trifluoromethylstyrene and N-(benzylidene) methylamine N-oxide were performed in the absence of solvent. Under microwave irradiation in a monomode Maxidigest Prolabo reactor, quantitative yields were obtained within 3 min. Compared to conventional heating under the same conditions, the yields are significantly increased (from 55%-64% to 88.98%). Classical conditions using boiling toluene (65% within 24-48 h) are now considerably improved.