Enantioselective Friedel-Crafts Alkylation between Nitroalkenes and Indoles Catalyzed by Charge Activated Thiourea Organocatalysts

Yang Fan, Steven R. Kass

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

A series of methylated and octylated pyridinium and quinolinium containing thiourea salts with a chiral 2-indanol substituent are reported. These organocatalysts are positively charged analogues of privileged bis(3,5-trifluoromethyl)phenyl substituted thioureas, and are found to be much more active catalysts despite the absence of an additional hydrogen bond donor or acceptor site (i.e., the presence of a heteroatom-hydrogen or heteroatom). Friedel-Crafts reactions of trans-β-nitorostyrenes with indoles are examined, and good yields and enantioselectivities are obtained. Mechanistic studies indicate that this is a second-order transformation under the employed conditions, and is consistent with the dimer of the thiourea being the active catalyst. Charged organocatalysts, consequently, represent an attractive design strategy for catalyst development.

Original languageEnglish (US)
Pages (from-to)13288-13296
Number of pages9
JournalJournal of Organic Chemistry
Volume82
Issue number24
DOIs
StatePublished - Dec 15 2017

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