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

• DOI: 10.1021/acs.joc.7b02411
• Publication Date: 2017-11-22T20:19:21Z
• Authors: Yang Fan; Steven R. Kass
• Keywords: Friedel–Crafts reaction

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