7-Azaindole derivatives, addition

The medicinal importance of 2-aryltryptamines led Chu and co-workers to develop an efficient route to these compounds (130) via a Pd-catalyzed cross-coupling of protected 2-bromotryptamines 128 with arylboronic acids 129 [137]. Several Suzuki conditions were explored and only a partial listing of the arylboronic acids is shown here. In addition, boronic acids derived from naphthalene, isoquinoline, and indole were successfully coupled with 128. The C-2 bromination of the protected tryptamines was conveniently performed using pyridinium hydrobromide perbromide (70-100%). 2-Phenyl-5-(and 7-)azaindoles have been prepared via a Suzuki coupling of the corresponding 2-iodoazaindoles [19]. 

Yet the reaction that attracted more interest has been the conjugate addition of arenes. It was first described by Hashmi in 2000 that enones and furans could react in the presence of AuCls. In the reported cases, furans were also formed by a gold-catalyzed reaction of allenones (equation 133). Electron-rich substituted benzenes also underwent 1,4-addition with Michael acceptors. Later, 7-azaindoles (equation 134) were shown to provide 3-alkylated derivatives. On the other hand, indoles (equation 135) reacted selectively... 

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