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Enhanced Efficiency of Thiourea Catalysts by External Brønsted Acids in the Friedel–Crafts Alkylation of Indoles
Author(s) -
MarquésLópez Eugenia,
Alcaine Ana,
Tejero Tomás,
Herrera Raquel P.
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201100506
Subject(s) - thiourea , friedel–crafts reaction , chemistry , alkylation , catalysis , brønsted–lowry acid–base theory , indole test , reactivity (psychology) , organic chemistry , selectivity , medicine , alternative medicine , pathology
A novel study on the influence of external Brønsted acids on thiourea catalysts in the asymmetric Friedel–Crafts alkylation of indoles with nitroalkenes is reported. The final 3‐substituted indole derivatives were synthesized with better results because of cooperative effects between the chiral thiourea and a Brønsted acid additive ( 1a· HA). The effects of diverse catalysts, different acid additives, solvents, and temperatures in the reaction were also explored. The high reactivity and selectivity of the reaction is presumptively attributed to an appropriate assembly between the Brønsted acid and the thiourea structure, affording a more acidic and rigid catalytic complex.