Reações de acoplamento da 8-iodo e 6-iodo-3,7,3',4'-tetrametoxi-quercetina paládio-catalisada com 2-metil-3-butin-2-ol e 2-metil-3-buten-2-ol

Abstract

This work describes a regioselectivity study of iodination by 3,7,3 ', 4'- tetramethoxy-quercetin (retusin) (7) to obtain the possible isomers that can be formed in this reaction. These products were used as electrophiles of the coupling reaction of Heck and Sonogashira. Regioselectivity study contemplates 21 different reactions. Reactions by protic polar solvent select the 8-iodine-retusin (9), standing out under the conditions of I2, LiOH, MeOH in 54% yield. The reactions by polar aprotic solvent or neat reaction select the 6-iodineretusin (8), standing out under the conditions of I2, K2CO3, without solvent with 60% yield. Within these 21 reactions, 5 were to obtain 6,8-diiodine-retusin (52), 3 being by retusin and 2 using as a limiting reagent the iodinated isomers. The best condition was the reaction by retusin, NIS, without solvent with 68% yield. Sonogashira coupling reactions were inconclusive because of the difficulty in the purification of the reactions, which still presents much different products. Heck coupling reactions by the butyl acrylate and the isomers were performed, obtaining two unpublished products in 66% yield (compounds 59 and 60) and the reaction of 2-methyl-3-buten-2-ol with 6-iodine-retusin (8) which formed two products, 61 and 62, in yields of 67% and 35%, respectively. There is acetilation by isomers, obtain 5-acetyl-6-iodine (63) and 5-acetyl-8-iodine-3,7,3',4'-tetramethoxy-quercetin (64). And benzylation by returin (7) and 8-iodo-retusin (9), obtain 5-benzyl (65) and 5-benzyl-8-iodine-3,7,3',4'-tetramethoxy-quercetin (66). All products were characterized by 1H and 13C NMR spectroscopy and mass spectrometry.