Synthesis of 3‐ and 6‐Sulfonylindoles from ortho‐Alkynyl‐N‐sulfonylanilines by the Use of Lewis Acidic Transition‐Metal Catalysts

Abstract

Gold-catalyzed reactions of ortho-alkynyl-N-sulfonylanilines produced the corresponding 3-sulfonylindoles in good to high yields. For example, the reaction of N-mesyl-N-methyl-2-(1-pentynyl)aniline, N-mesyl-N-methyl-2-(phenylethynyl)-aniline, and 2-ethynyl-N-mesyl-N-methylaniline in the presence of 10 mol % of AuBr3 in toluene at 80 degrees C gave 3-mesyl-1-methyl-2-propylindole, 3-mesyl-1-methyl-2-phenylindole, and 3-mesyl-1-methylindole in 95, 92, and 71% yield, respectively. Furthermore, we found that the reactions of 2-alkynyl-6-methoxy-N-sulfonyl-anilines in the presence of indium catalyst (InBr3) afforded the corresponding 6-sulfonylindoles as the major product in good yields. For example, the reaction of 6-methoxy-N-methyl-2-(1-pentynyl)-N-tosylaniline in the presence of 5 mol % of InBr3 in toluene at 80 degrees C gave an 87:13 mixture of 7-methoxy-1-methyl-2-propyl-6-tosylindole and 7-methoxy-1-methyl-2-propyl-3-tosylindole in 95% yield. Most probably, the gold-catalyzed reactions of ortho-alkynyl-N-sulfonylanilines proceed through a [1,3] sulfonyl migration, whereas the indium-catalyzed cyclizations of 2-alkynyl-6-methoxy-N-sulfonylanilines, which produce 6-sulfonylindoles, proceed by an unprecedented [1,7] sulfonyl migration.

Metalltriflimidate sind bessere Katalysatoren für die organische Synthese als Metalltriflate – der Effekt eines stark delokalisierten Gegenions

“…Eine Gemeinsamkeit dieser Reaktionen ist die selektive 1,3-Verschiebung der labilen Gruppe am Heteroatom unter Bildung eines Alkenylmetall-Intermediats in einem Prozess, der dem in Schema 20 gezeigten ähnelt. [118][119][120] Kürzlich wurde eine alternative Strategie entwickelt, die auf der schwierigeren 1,2-Verschiebung beruht. Aus den g-Lactamen 23, die sich von ortho-Alkinylanilin ableiten, konnten die an ein cyclisches Keton anellierten Indolderivate 24 über eine Sequenz aus metallkatalysierter Cyclisierung, 1,2-Acyl-Verschiebung und Homogene Katalyse Angewandte Chemie abschließender 1,2-Verschiebung der R'-Gruppe erhalten werden.…”

Synthesis and functionalization of 3-bromo-2-(2-chlorovinyl)benzothiophenes as molecular tools

“…18) allowed the coupling to proceed efficiently between (E)-8b and ortho-substituted arylalkynes to provide (E)-enynes 12 and 13 in good yields (Scheme 6). Taking advantage of the structure of enyne (E)-13 having an ortho-N-tosyl-N-methylaniline function, we achieved a goldcatalyzed cyclization 19 to give, aer tosyl migration, 2-alkenyl-3-sulfonylindole (E)-14 in 90% yield. We further demonstrated that the C-Cl bond in (E)-8b can react with a Grignard reagent (EtMgBr) in the presence of a catalytic amount of Fe(acac) 3 (ref.…”

π-Conjugated carbocycles and heterocycles via annulation through C-H and X-Y activation across CC triple bonds

“…-substituted indoles 9, in which the alkenyl group originated from R of alkyne. [77][78][79] Gold(III) or In(III)-catalyzed reaction of ortho-alkynyl-N-sulfonylanilines 10 produced 3-sulfonylindoles 11; [80][81] under certain conditions accompanied by the formation of 6-sulfonylindoles. Platinum(II)-olefin-catalyzed reaction of ortho-alkynylphenyl acetals 12 gave 3-(1-alkoxyethyl)-2-alkylbenzofurans 13 in high yields (Scheme 4).…”