Aplicação de sonoquímica na tioesterificação e amidação de benzoxa(tia)zóis

Abstract

This work describes the systematic synthesis of fourteen tioesters derived from 2-mercaptobenzoxazoles and 2-mercaptobenzothiazoles from acylation reaction of acyl chlorides (R1C (= O) Cl where R1 = C6H5, 4-CH3C6H4 , 2-OCH3C6H4, 4-OCH3C6H4, 2-FC6H4, 3-FC6H4, 4-NO2C6H4) and seven amides derived from reaction of 2-aminobenzothiazol with the same acyl chlorides. Among these twenty-one derivatives, this works described new techniques for the synthesis of eight novel compounds. Besides the conventional method, that transfer heat by heating the reaction flask, were also employed ultrasound and microwave irradiation. Sonication was performed in ultrasound reactor model VC 500, 500Watts, frequency 20KHz, 220 VOLTZ, using a probe of 13mm (1 / 2 inch, 10-250 mL, high intensity, magnitude greater than 100, length 139 mm) and microwave performed in a oven Piccolo Panasonic Model NN-S42BK of 20L, 220v-60Hz (frequency of 2.450MHz and a microwave power of 800W output and consumption of 1.400W). The yields obtained by ultrasonic irradiation were higher than the other methods tested (81-98%) with a reaction time of smaller (5 minutes) with a glass reactor system with open and monitoring the heat generated. Both analytical and spectral data (1H and 13C) and melting points of all compound are in full agreement with the proposed structures helped us to assign the correct signals of compounds