Consecutive Gold(I)-Catalyzed Cyclization Reactions of o-(Buta-1,3-diyn-1-yl-)-Substituted N-Aryl Ureas: A One-Pot Synthesis of Pyrimido[1,6-a]indol-1(2H)-ones and Related Systems

Abstract

Treatment of readily available o-(buta-1,3-diyn-1-yl-)-substituted N-aryl ureas such as 1 with the Au(I)-catalyst 11 affords, via a twofold cyclization process, the isomeric pyrimido[1,6-a]indol-1(2H)-one 3 in good yield.

Synthesis of Polycyclic Indole Skeletons by a Gold(I)‐Catalyzed Cascade Reaction

“…(5)]. According to the results described above and previous results from the literature [7,9] a plausible mechanism [10] that accounts for the gold(I)-catalyzed cascade reaction is depicted in Scheme 2. In a first step, the triple bond is activated by p-coordination of the gold(I) catalyst.…”

“…Ph 3 PAuCl/AgNTf 2 was also examined but just gave trace amounts of 4 a (Table 1, entry 7). Different silver salts were then tested in combination with IPrAuCl, but no im-provement was achieved (entries [8][9][10]. We then examined different solvents (Table 1, entries [11][12][13]).…”

A practical Cu(I)-catalyzed domino approach to 1,2-disubstituted indoles and its application for the assembly of indolophenanthridines

“…[17][18][19] In spite of these remarkable progresses, many of the previous methods require expensive and/or sensitive catalysts (such as Pd and Au salts) or special substrates such as 1-or 2-substituted indoles and o-(gem-dihalovinyl)anilines. The annulation of N-substituted 2-alkynylanilines [20][21][22] and the coupling/cyclization of 2-alkynyl halobenzenes with primary amines [23][24][25] can also generate 1,2-disubstituted indoles. Katz's group utilized the tandem substitution/cyclization to furnish 2-substituted N-arylindoles, but the protocol was limited to the reactions of 2-alkynylfluorobenzenes.…”

Formal [4+2] Reaction between 1,3‐Diynes and Pyrroles: Gold(I)‐Catalyzed Indole Synthesis by Double Hydroarylation

“…A related transformation involving the Ru-catalyzed annulation of pyrroles has been developed, but this process requires pent-1-en-4-yn-3-ol derivatives as the C4 synthon (Scheme 1 c). [6] Compared with isolated alkynes, [7,8] the use of gold catalysis with conjugated diynes, [9,10] especially for intermolecular reactions, stands at the very beginning. We designed a new Type 8 indole synthesis based on the gold(I)-catalyzed intermolecular formal [4+2] reaction between 1,3-diynes and pyrroles, which could be used to provide convenient access to 4,7-disubstituted indoles.…”