Peculiarities of the behavior of succinyl dichloride in Friedel-Crafts reaction with thiophenes*

Abstract

Keywords: 4,4-di(2-thienyl)but-3-enoic acids, 4,4-di(2-thienyl)butyrolactones, 4-oxo-4-(2-thienyl)butyric acids, succinyl dichloride, 1,4-(2-thienyl)butane-1,4-diones, thiophenes, acylation.1,4-Di(2-thienyl)butane-1,4-diones are convenient starting materials for the preparation of 2,5-di(2-thienyl)pyrroles, -furans, and -thiophenes which, in turn, can serve as precursors of polymers and monomers which show electrical conductivity and particular photochemical properties [1]. The known syntheses of 1,4-dihetarylbutane-1,4-diones are very varied. With regard to the most frequently used of these, the Stetter method is based on a Michael addition of aldehydes to the activated double bond of enones in the presence of cyanide or thiazolium salt [2,3]. Particularly promising for the preparation of unsymmetrical 1,4-diketones (although somewhat time consuming) is the method due to Kulinkovich et al. based on the reaction of methyland -bromomethyl ketones [4]. The reactions of diesters or N,N,N',N'-tetrasubstituted succinic acid diamides with hetaryl lithium [5] or reaction of sodium acetylide with hetarenecarbaldehydes and subsequent conversion of the 1,4-dihetarylbut-2-en-1,4-diol to the corresponding 1,4-diketone in the presence of alcoholic alkali solution [6] are relatively simple but they give low yields.We consider in more detail the data available for the Friedel-Crafts reaction of thiophene 1a, 2-methylthiophene 1b, and 2-bromothiophene 1c with succinyl dichloride (SDC) as the method for synthesizing the di(2-thienyl)-1,4-dione 2a and the substituted bis(5-methyl-2-thienyl)-1,4-dione 2b, and bis(5-bromo-2-thienyl)-1,4-dione 2c, respectively. This apparently simple and obvious route meets a series of complications, _______ * Dedicated to the memory of an outstanding heterocyclic chemist and unsurpassed editor, Alexey Nikolaevich Kost,

Non-Acidic Mediated Friedel-Craft Reaction of Thiophene Using EtAlCl2

“…Although several catalysts are now available as mentioned above, there have been sustained efforts towards the finding of new catalysts. Recently, Simirnov et al reported the preparation of 1,4-bis(2thienyl)butane-1,4-dione with SnCl4, TiCl4 and AlCl3 catalysts 8 . Although alkyl Lewis acids are weaker than common Lewis acids (AlCl3, FeCl3, etc.…”