Palladium-Catalyzed Carbon-Heteroatom Bond Formation with Alkynes

Palladium-Catalyzed Carbon-Heteroatom Bond Formation with Alkynes 

Larock reported his initial results in this area in 1991, in the reaction of ortho-iodoanilines with internal alkynes [58]. This method provides an efficient route to assembly of the 2,3-disubstituted indole core from anilines and alkynes, both of which are easily generalized. This initial report employed N-protected anilines, however, subsequent research demonstrated that the parent aniline moiety can also participate in this chemistry [59]. 

R = alkyl, aryl, COOMe, alkynyl R = alkyl, aryl, alkenyl 

While this cyclization method does not allow the incorporation of substituents into the 3-position, as is available with internal alkynes, in analogous chemistry to that in Section 6.2.2, the palladium bound intermediate of cyclization can be intercepted with a range of external reagents to functionalize this site. These include aryl or vinyl halides, allylic substrates, carbonylation, and Heck coupling with alkenes [72]. 

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