Calcogenação eletrofílica de oximas β,γ-insaturadas para síntese de 4,5- isoxazolinas

Abstract

The present report describe the cyclization of β,γ-unsaturated oximes using electrophilic chalcogenide species, aiming specially in organic molecules containing selenium and tellurium. The synthesis of isoxazolines 3f-s was performed using acetonitrile as the solvent, aril calcogenil halides 2 and β,γ-unsaturated oximes 1. Using this protocol 6 isoxazolines containing selenium were prepared with yields ranging from 11-82%. Isoxazolines containing tellurium were also synthetized from the respective iodide, which 7 isoxazolines were synthetized with yields from 36 to 77%. In an alternative fashion ditellurides 3u-v also were synthethized starting rom the tellurium tetrachloride and β,γ-unsaturated oximes 1, followed by the addition of sodium borohydride in a mixture of water/THF and a ir oxidation. Ditellurides were obtained in yields that ranged from 44-67%. In total 17 compounds were obtained, regarding that all the tellurium derivatives are unprecedented. Aiming to eliminate exhausting purification steps and due to the low solubility of the product in hexanes all the compounds were treated, by adding and removing hexanes from the crude, to obtain the pure product. Being an alternative method for column purification.