TY - JOUR
T1 - Enantioselective Friedel-Crafts Alkylation between Nitroalkenes and Indoles Catalyzed by Charge Activated Thiourea Organocatalysts
AU - Fan, Yang
AU - Kass, Steven R.
N1 - Funding Information:
Generous support from the National Science Foundation (CHE-1361766 and 1665392) is gratefully acknowledged.
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/12/15
Y1 - 2017/12/15
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.joc.7b02411
DO - 10.1021/acs.joc.7b02411
M3 - Article
C2 - 29166016
AN - SCOPUS:85038421928
SN - 0022-3263
VL - 82
SP - 13288
EP - 13296
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
IS - 24
ER -