Carboxylic Acids as Traceless Directing Groups for the Rhodium(III)‐Catalyzed Decarboxylative CH Arylation of Thiophenes

Abstract

A rhodium(III)-catalyzed carboxylic acid directed decarboxylative C À H/C À H cross-coupling of carboxylic acids with thiophenes has been developed. With a slight adjustment of the reaction conditions based on the nature of the substrates, aryl carboxylic acids with a variety of substituents could serve as suitable coupling partners, and a broad variety of functional groups were tolerated. This method provides straightforward access to biaryl scaffolds with diverse substitution patterns, many of which have conventionally been synthesized through lengthy synthetic sequences. An illustrative example is the onestep gram-scale synthesis of a biologically active 3,5-substituted 2-arylthiophene by way of the current method.

Iridium‐Catalyzed Annulation Reactions of Thiophenes with Carboxylic Acids: Direct Evidence for a Heck‐type Pathway

“…[7][8][9] Among these mechanisms,the S E Ar and CMD pathways have been generally accepted, and the reactions usually occur at the most nucleophilic a-position of the thiophene ring. [7][8][9] Among these mechanisms,the S E Ar and CMD pathways have been generally accepted, and the reactions usually occur at the most nucleophilic a-position of the thiophene ring.…”

“…[11] Reactions of 2-aryl thiophenes bearing av ariety of functional groups,such as fluoro,chloro,trifluoromethyl, acetyl, or ester moieties,a lso proceeded in moderate yields (7e-7j). [8] To obtain aclearer picture of the reaction, several control experiments were performed. Tables 2a nd 4p roceed under very similar reaction conditions,t he selectivity to the spiro products could be related to the substrate itself.T his finding together with the above transformation to give coumarin-type frameworks suggests that the thiophenes might react through aHeck-type pathway,which is distinctly different from the S E Ar and CMD pathways encountered in the well-described oxidative CÀH/CÀHc ross-coupling reactions of thiophenes with other heteroarenes.…”

Regioselective Synthesis of Polycyclic and Heptagon‐embedded Aromatic Compounds through a Versatile π‐Extension of Aryl Halides

“…Indeed, the regioselective synthesis of planar aromatic systems remains along-standing challenge and most methods are prone to the use of symmetrical reagents [5][6][7][8] such as alkynes [8d, 9] or ortho-TMS aryl triflate-generated arynes (Scheme 1b). [12f] Recently,the use of acarboxylic acid as traceless directing group has received significant attention [14] and Hongsg roup recently demonstrated this strategy with an impressive tandem synthesis of acenes (Scheme 1c). [12f] Recently,the use of acarboxylic acid as traceless directing group has received significant attention [14] and Hongsg roup recently demonstrated this strategy with an impressive tandem synthesis of acenes (Scheme 1c).…”

Palladium(II)‐Catalyzed Tandem Synthesis of Acenes Using Carboxylic Acids as Traceless Directing Groups

“…[10] Recently, the use of carboxylic acids as traceless directing groups for decarboxylative coupling was investigated as a highly efficient route for the synthesis of diversely substituted arenes. [11,12] We were intrigued by the possibility of a tandem transformation employing removable carboxylic acid directing groups, which simultaneously afforded catalytic control and efficiency. In particular, we speculated that the olefinated intermediate generated in situ as a result of the Pd(II)-catalyzed, carboxyl-directed alkenylation of a diaryl carboxylic acid, could be further utilized for another C-H activation in the context of the same directing group.…”