Organic Chemistry: Current Research
Open Access

Stille reaction of β-nitro and β-tosyl substituted styryl bromides

3^rd International Conference on Organic and Inorganic Chemistry

July 17-19, 2017 Chicago, USA

Antonio J Zapata V

Universidad de Guayaquil, Ecuador

Posters & Accepted Abstracts: Organic Chem Curr Res

Abstract :

The palladium-catalyzed coupling of organostannanes with organic electrophile (Stille reaction) has become an important synthetic tool in organic chemistry (eq. 1). Several years ago, we became interested in applying the Stille reaction to �±-stannyl-�±, �²-unsaturated carboxylic esters. We found that these esters reacted with acid chlorides to afford good yields of coupling products (eq. 2). However, the reaction failed when it was attempted with vinylic bromides or iodides. We hypothesized that this result could be changed by reversing the roles of the reactants in the coupling process. Thus, a study of the Stille coupling of a series of functionalized styryl bromides with 1-propenyltributyltin was undertaken (eq. 3). This reaction afforded low to moderate yields of 1, 3-dienes. Interestingly, the best yield of product was obtained using methyl �±-bromocinnamate, the styryl bromide substituted with the more electron-withdrawing group (R=CO2Me). Consequently, we decided to examine the Stille reaction of �²-nitro and �²-tosyl (�²-(p-MeC6H4SO2)) substituted styryl bromides (eq. 4). The �²-bromo-�²-nitro-styrenes 1 and 2 reacted with a variety of organostannanes using bis (acetonitrile) dichloropalladium (II) as catalyst and n-methyl-pyrrolidinone (NMP) as solvent at room temperature. Good yields of 2-nitro-1, 3-dienes were obtained as a mixture of isomers. The Stille reaction of �²-bromo-�²-tosyl-styrenes 3 and 4 was also investigated. In this case, the best yields of coupling products were obtained using an excess of organotin compound (1.5 equivalents), a mixture of bis (acetonitrile) dichloropalladium (II) (5% molar) and copper iodide (10% molar) as catalysts and NMP as solvent at room temperature. Again, good yields of products, as a mixture of isomers, were obtained. The Stille reactions of �²-nitro and �²-tosyl substituted styryl bromides reported here constitute an useful synthetic tool towards the preparation of functionalized 1, 3-dienes. These unsaturated molecules are among the most versatile organic compounds which participate in a wide variety of applications, including fine chemical synthesis and polymer chemistry.

Biography :

Email: antonio.zapatav@ug.edu.ec