Larock synthesis internal alkyne annulation

Roesch, K. R., Larock, R. C. Synthesis of lsoindolo[2,1-a]indoles by the Palladium-Catalyzed Annulation of Internal Alkynes. Org. Lett. 

The scope and mechanism of palladium-catalyzed annulation of internal alkynes to give 2,3-disubstituted indoles, the effect of substituents on the aniline nitrogen or on the alkynes, as well as the effect of the salts such as LiCl or n-BuaNCl were studied by Larock and coworkers (1998 JOC7652). The mechanism they propose for indole synthesis proceeds as follows (a) reduction of the Pd(OAc)2 to Pd(0) (b) coordination of the chloride to form a chloride-Ugated zerovalent palladium species (c) oxidative addition of the aryl iodide to Pd(0) (d) coordination of the alkyne to the... 

The synthesis of l,6-dihydropyrrolo[2,3- ]indazole derivatives 27 has been described. The indoHc ring system was constructed via a Larock palladium-catalyzed annulation using terminal and internal alkynes (Scheme 17). 

Larock, R. C., Kadnikov, D. V. 2000. Synthesis of coumarins via palladium-catalyzed carbon-ylative annulation of internal alkynes by o-iodophenols. Org. Lett. 2 3643-3646. 

Kadnikov, D.V. and Larock, R.C. (2003) Palladium-catalyzed carbonylative annulation of internal alkynes synthesis of 3,4-disubstituted coumarins. The Journal of Organic Chemistry, 68, 9423-9432. 

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