LiClO₄-Catalysed C-Alkylation of Pyrrole and Indoles with Aziridines and Epoxides

Abstract

Aryl- N-tosylaziridines and epoxides smoothly undergo ring-opening with pyrrole and indoles in the presence of 5M lithium perchlorate in diethyl ether (LPDE) at ambient temperature to afford the corresponding 2- and 3-alkylated pyrroles and 3-alkylated indoles in high yields with high selectivity. LiOTf is also found to be an effective catalyst for this transformation.

Catalytic Enantioselective Friedel–Crafts Alkylation of Indoles with Nitroalkenes by Using a Simple Thiourea Organocatalyst

“…All reactions occurred without any loss in the enantiomeric enrichment of the products, and the relative stereochemistry of 7 was tentatively assigned as 1,4‐ trans by means of NOE experiments. Furthermore, the formation of the sulfonamide derivative 6 allowed the assignment of the absolute configuration of the catalytic product 4 a as 2 R , from the comparison of its optical rotation and HPLC retention time with those of an authentic sample of ent ‐ 6 (in 94 % ee ), which was synthesized by the ring‐opening at the benzylic position of (2 S )‐2‐phenyl‐1‐ p ‐toluenesulfonyl aziridine19 with indole 2 a promoted by LiClO 4 20…”

In situ preparation of a ferric polymeric aluminum chloride–silica gel nanocatalyst by mechanical grinding and its solid-phase catalytic behavior in organic synthesis

“…This effectively overcomes the potential ecological hazards arising from the use of novel environmentally toxic surfactants (SDS, SDBS, etc.). 13 In fact, it was reported in the literature that RuCl 3 ÁnH 2 O as catalyst could give the 3-alkylindole product in 82% yield in the absence of solvent, but the amount of ethylene oxide fed was greatly excessive (3.7 times that of the indole substrate); not only the expensive precious metal salt catalyst was used in large amounts (5 mol %) and difficult to recover, but also the reaction time was as long as 6 h. 31 In traditional liquid phase solvents (CH 2 Cl 2 and CH 3 CN), the catalysts that efficiently catalyse the nucleophilic ring-opening reaction of indole and styrene oxide are LiClO 4 , 32 InCl 3 33 and other expensive waterresistant catalysts. [34][35][36] The degree of greenness is extremely low and it is difficult to promote application.…”

Palladium(II)‐Catalyzed C3‐Selective Friedel–Crafts Reaction of Indoles with Aziridines

“…Whereas the ring‐opening of aziridines with heteroatomic nucleophiles, such as alcohols, amines, thiols, and azides, is widespread,– the Friedel–Crafts reaction of electron‐rich arenes is less well‐developed –. In an early report, LiClO 4 was shown to efficiently promote this reaction, but with limited substrate scope, whilst the use of InCl 3 as a catalyst gave the products as a mixture of regioisomers . A dual‐catalyst system that consisted of Sc(OTf) 3 /Zn(OTf) 2 (Tf=trifluoromethanesulfonyl) was used in a single example of a ring‐opening reaction between aziridines and indoles, but the product was accompanied by an unidentified by‐product .…”