Ruthenium-catalyzed indole ring synthesis

Several of the rhodium-catalyzed indolizations previously presented (Chapter 81) are equally accomplished with ruthenium. An example is the deoxygenation of 2-nitrostil-bene to 2-phenylindole with Ru (CO) [1], The use of 

Indole Ring Synthesis From Natural Products to Drug Discovery, First Edition. Gordon W. Gribble. 2016 John Wiley Sons, Ltd. Published 2016 by John Wiley Sons, Ltd. 

Tokunaga and Wakatsuki reported a one-pot indole synthesis from anilines and propargyl alcohols using Rn3(CO)j2 [5], and Nicholas and colleagues reported a Ru-catalyzed indole synthesis via the reductive annulation of nitros-oarenes with alkynes (equation 3) [6, 7]. Saa and coworkers described the Ru-catalyzed cycloisomerization of o-alkynylanihnes (equation 4) [8, 9]. Nissen and Detert reported a total synthesis of lavendamycin that featnred a Ru-catalyzed [2-f2-f2] cycloaddition of an o-alkynyl-ynamide, a method that was superior to rhodium catalysis both in terms of efficiency and regiochemistiy [10]. 

An obvious and efl ective use of ruthenium was ring-closing metathesis with the two mthenium-containing Gmbbs catalysts. The groups of Arisawa and Nishida [16], 

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