Synthesis of Indoles from 2-Azidoacrylate and ortho-Silyl Aryltriflates

Significance

Reported is an efficient synthesis of substituted indoles 3 from the CsF- and Ph₃P-mediated reaction of 2-azidoacrylates 1 with ortho-silyl aryltriflates 2. The reaction involves the formation of iminophosphorane (detected by HRMS and ^³¹P NMR spectroscopy) and benzyne intermediates and subsequent annulation-hydrolysis-air oxidation. After screening of solvent and Ph₃P loading, the scope of this reaction was demonstrated for various ethyl 2-azidoacrylates 1 and substituted ortho-silyl aryltriflate 2. 1,2-Naphthalyne and ortho-MeO benzyne precursors were shown to provide a single product, respectively, whose structures were confirmed by X-ray analysis.