Synthesis of Benzothiophenes via 3 2 Cycloaddition Reactions

Indoles represent a very important and unique class of fused five-membered heterocyclic compounds and are probably the most prevalent among other heterocyclic frameworks broadly found in nature. The indole ring system is incorporated 

Following the original report by Castro vide supra), many other research groups utilized ortho-alkynylanilines as versatile substrates in transition metal-catalyzed 

Following these reports, Dai and coworkers disclosed a microwave-assisted solid-phase-supported synthesis of C5-substituted indole [168] derivatives using Hiroya s Cu(II)-conditions [202]. 

Similarly, excellent yields of indole products were achieved when employing catalytic amounts (5 mol%) of phenylmercuric triflate. This finding led to the development of a solid-supported silaphenylmercuric triflate catalyst, which allowed indole synthesis with high efficiency in a flow reactor [204]. 

Kobayashi reported that the microencapsulated Au(III) salt supported on silica gel could serve as a very efficient catalyst for this transformation, providing good to excellent yields of differently C2-monosubstituted indoles at room temperature with little or no detectable gold leaching [207]. 

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