Study On The Synthesis Of Chiral 3-(ethylthio)butanal And Its Derivatives

Small molecule organic catalysts with its own merits, have been recognized by researchers and become a research focus at the present stage. More prominent in this regard is the catalyst for the class of proline and its derivatives, their asymmetric C-C bond, C-N bond, C-S bond formation reactions, such as the Aldol reaction, Michael reaction played a significant role.Clethodim herbicide is a new good, has been widely used. John Whittington, who found that l-configuration of clethodim is surprisingly more effective in regulating the growth of grass plants than the corresponding racemic mixture or the optically pure (L)-enantiomer. And they prepared a single hand of clethodim by a preparative HPLC column.In this paper, we discuss the study synthesis of chiral(S)- 3-(ethylthio)butanal and its Derivatives. We discss the main two steps : The first is the Synthesis of chiral (S)-3-(ethylthio)butanal. In this step, we first synthesized catalysts 1-3, and also used catalysts 4-6 which were prepared by Dr.lin jian. We investigated the application of catalysts for asymmetric Michael addition reaction between crotonaldehyde and ethanethiol. We selected the best catalyst 2, by which we investigated the reaction temperature,reaction solvent effect,and ultimately determine the best conditions. Under these conditions, we can get the product with 91% ee and 82% yield. The second we synthesize Chiral 6-ethylthio-3-heptene -2-one, we used two synthetic routes. First, the 3-(ethylthio)butanal and ethyl acetoacetate in the pyrrolidine and other organic base catalyst, occur Knoevenagel reaction. After we obtain product by hydrolysis of keto-type. Unfortunately, this line did not achieve the desired effect . Line 2, 3-(ethylthio)butanal and acetone asymmetric occurr Aldol reaction. First we try the proline, List and others reported as acetone as solvent and at 0℃, the self-condensation of aliphatic aldehydes has been inhibited, aldehydes and ketones occurs only asymmetric Aldol reaction, and received only two addition Product:α-hydroxy ketones andα,β-unsaturated ketone. The latter is exactly what we want results, while the former has been the latter through dehydration. We have also added to the reaction system, a small amount of methanol to increase the solubility of proline, thus shortening the reaction time increased the yield of reaction. Second, we use solid sodium hydroxide to catalytic reaction. See the strong sodium oxide highly, along with a lot of byproducts. Second, we use solid sodium hydroxide to catalytic reaction. See the strong sodium oxide highly, along with a lot of byproducts,we only get the product of low yield rate. Through the TLC detection, we obtained the mostlyα-hydroxy ketone compounds. Again we get the target product by concentrated phosphoric acid.Finalized through the line of the second experiment, to proline as the catalyst we began to test the continuous synthesis of (S) -6 - ethylthio -3-heptene -2-one, but the result is not ideal. Aspects of yield and ee value of further research is required to improve, but they work for the chiral synthesis of clethodim laid a good foundation.