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Synthesis of Polycyclic Indole Skeletons by a Gold(I)‐Catalyzed Cascade Reaction
Author(s) -
Wang Tao,
Shi Shuai,
Pflästerer Daniel,
Rettenmeier Eva,
Rudolph Matthias,
Rominger Frank,
Hashmi A. Stephen K.
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201303539
Subject(s) - chemistry , catalysis , hydroamination , indole test , cascade reaction , intramolecular force , nucleophilic substitution , nucleophile , nucleophilic addition , enantiopure drug , cycloisomerization , combinatorial chemistry , organic chemistry , enantioselective synthesis
The conversion of simple, easily available urea‐substituted 3‐phenylpropargyl alcohols catalyzed by a simple IPr–gold(I) catalyst in a gold(I)‐catalyzed cascade reaction composing of a gold‐catalyzed nucleophilic addition and a subsequent gold‐catalyzed substitution reaction delivers 1 H ‐imidazo[1, 5−a]indol‐3(2 H )‐ones. Other gold(I) catalysts or silver catalysts gave lower yields and often gave other side products. Gold(III) and copper(II) catalysts decomposed the starting material. Twelve examples, including donor and acceptor substituents on the distal nitrogen of the urea substructure, are provided. An X‐ray crystal structure analysis confirmed the structural assignment. The mechanistic investigation including isolation and further conversion of intermediates and reactions with enantiopure starting materials indicated that after the nucleophilic‐addition step, the substrate undergoes an S N 1‐type benzylic substitution reaction at the indolyl alcohol intermediate or an intramolecular hydroamination reaction of the 2‐vinylindole intermediate.