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Fe(OTf) 3 : An Efficient Catalyst for Michael Addition Reactions of Homoaromatic C‐H Nucleophiles with Nitrostyrenes under Microwave Irradiation in Solvent‐Free Condition
Author(s) -
Bhuyan Pubanita,
Bhuyan Amar J.,
Nyodu Mimik,
Chelleng Nilamoni,
Saikia Lakhinath
Publication year - 2019
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201803497
Subject(s) - nucleophile , michael reaction , regioselectivity , catalysis , alkylation , solvent , adduct , chemistry , microwave irradiation , acceptor , organic chemistry , physics , condensed matter physics
Available procedures for Michael addition reaction of homoaromatic C−H nucleophiles ( N,N ‐dialkylanilines and their cyclic analogues) with nitrostyrenes are observed to be very time consuming (18‐72 h). So, a gentle effort has been made to reduce the time requirement, which is reported herein. Our developed methodology makes use of commercially available Fe(OTf) 3 as an efficient catalyst (5 mol%) under microwave irradiation (700 W, 120 °C) and solvent‐free condition and found to be capable of furnishing the Michael adducts in 40–98% yields within 10–20 minutes (19 examples). The regioselectivity of addition of N,N ‐dialkylanilines and their cyclic analogues to nitrostyrene derivatives is observed to be exclusively para . The methodology can be extended to the use of cinnamaldehyde as Michael acceptor (2 examples). Three of our Michael addition products are denitrohydrogenated to achieve their corresponding alkylated arenes which paves an effective two‐step synthetic route for p‐ alkylated N,N‐ dilalkylanilines. Ability to reduce the time requirement by a huge margin (from days to minutes), exclusion of solvent system, exclusive para addition of the homoaromatics to nitrostyrenes are the features of attraction of the developed methodology. The proposed two‐step procedure for regioselective synthesis of p‐ alkylated N,N ‐dialkylanilines should attract readers’ attention.