Indole-3-carboxylic acid doubled

The bond between the nitrogen and the carbonyl group of A-aryl benzamides possesses sufficient double-bond character that these compounds will also undergo 6-7t electrocyclic closure [88]. The reaction is quite general and occurs for anilides of indole carboxylic acids, as shown in Scheme 44 [89]. The reaction also proceeds if the A-phenyl group is replaced by a pyridine ring [89d] or a vinyl group [90]. 

Catellani [61] reported a palladium/norbomene-catalyzed synthesis of heteroatom-containing o-teraryls from aryl iodides and heteroarenes (including indoles and pyrroles) through double C-H arylation. Fagnou s group [62] applied their own protocol (Pd(II)/Ag(I)/carboxylic acid) to achieve the direct arylation of azaindoles. Itami [63] demonstrated the first iridium-catalyzed C-H arylation of heteroarenes (involving indoles and pyrroles) with aryl halides. 

Zhang et al. effected palladium-catalyzed oxidative C3-vinylations of indol-izine-l-carboxylates 136 with various styrenes (Scheme 10.45)."° Use of the bidentate nitrogen ligand bipy was key to formation of the branched a-product regioisomer 137 over the linear P-product. The authors later demonstrated that the same indolizine-l-carboxylates could be C3-acylated with a variety of a,P-unsaturated carboxylic acids via C—H and C—C double bond cleavage under oxidative conditions (138). "... 

---