Alilação do tipo Barbier de Aldeídos aromáticos promovida por Zn e catalisada por L-Prolina em meio aquoso

Abstract

Given the various strategies to form C-C bonding, involving organometallic intermediates, the Barbier reaction has proved to be an important methodology that can be performed efficiently in aqueous media with several advantages.The use of organocatalysts has also been very advantageous in various chemical reactions to a synthesis of safe and environmentally correct products.In this work, synthetic methodologies were studied to obtainhomoallyl alcoholsby means of alilation of the Barbier type. In order to follow the principles of green chemistry, the method relies on allylation reactions from aromatic aldehydes, allyl bromide, zinc and L-proline as catalyst, using water as the solvent. Aromatic aldehydes with allyl bromide, zinc and a 20% L-proline as catalyst were tested, being 4-F-benzaldehyde, 4-OMe-benzaldehyde and 2-naphthaldehyde using water as the solvent. Secund, the increase in the amount of L-proline to 80% was added and 3 aromatic aldehydes were tested, being 4-F-benzaldehyde, 2-OH-benzaldehyde and 2-OMe-benzaldehyde with allyl bromide, zinc and water. All data were previously monitored by CG-FID and CCD and the homoallyl alcoholswere characterized from the respective signals by GC-MS, throughcomputerized comparison of the library masses of the apparatus itself and the specific fragmentation pattern.In the first 3, with 20% L-proline, excellent conversions were detected, but 4-F-benzaldehyde was fully converted to 1-(4-fluorophenyl) but-3-en-1-ol with only 1h of magnetic stirring , 4-OMe-benzaldehyde converted to 1-(4-methoxyphenyl) but-3-en-1-ol with 4h and 2-naphthaldehyde converted to 1-(2-naphthyl) but-3-en-1-ol with 1h, in all cases, without formation of by-products. Subsequently, in the last 3 assays, with 80% proline L, the reaction time of 4-F-benzaldehyde was reduced to 30 minutes with complete conversion of the 1-(4-fluorophenyl) but-3-en-1-ol alcohol; 2-OH-benzaldehyde and 2-OMe-benzaldehyde were converted respectively into 1-(2-hydroxyphenyl) but-3-en-1-ol and 1-(2-methoxyphenyl) but-3-en-1, however, traces of the starting materials were still detected. The 1-(4-fluorophenyl) but-3-en-1-ol and 1-(2-naphthyl) but-3-en-1-ol alcohols were also characterized by 1 H and ¹³C NMR.