Novel Base‐Free Catalytic Wittig Reaction for the Synthesis of Highly Functionalized Alkenes. Issue 7 (13th January 2016)

• Record Type: Journal Article
• Authors: Schirmer, Marie‐Luis; Adomeit, Sven; Spannenberg, Anke; Werner, Thomas
• Is Part Of: Chemistry. Volume 22:Issue 7(2016)
• Page Start: 2458
• Page End: 2465
• Publication Date: 2016-01-13
• Subjects: homogeneous catalysis -- olefination -- organocatalysis -- Wittig reactions -- ylides; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201503744
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: A highly efficient catalyst system for base‐free catalytic Wittig reactions has been developed and optimized. Initially, several potential (pre)catalysts as well as different silanes as reducing agents were screened. A system based on a readily available phosphine oxide as precatalyst and trimethoxy silane as reducing agent proved to be optimal. The effect of various Brønsted acidic additives was studied. Subsequently, the reaction conditions were optimized and standard reaction conditions were determined. Under these conditions the scope of this new protocol was evaluated. Nine activated olefins and 33 aldehydes were converted into 42 highly functionalized alkenes. Notably, aromatic, aliphatic as well as heteroaromatic aldehydes could be converted, giving the desired products in isolated yields up to 99 % and with good to excellent E / Z selectivities. These results underline the remarkable efficiency of this protocol considering the complexity of the reaction mixture and the four reaction steps that proceed in parallel in one pot. Abstract : Drop the base : A novel catalytic system based on a readily available phosphine oxide precatalyst for base‐free catalytic Wittig reactions has been developed (see scheme). Under the optimized reaction conditions, numerous functionalized alkenes were prepared in yields up to 99 % and with good to excellent E / Z selectivities.