Reviews and Accounts ARKIVOC 2013 (i) 470-535
reactions can be divided into condensation reactions, Michael addition reactions, as well as reactions with nitriles, alcohols, and halogenated compounds.
2.1. Condensation reactions 2.1.1. Knoevenagel condensations. Condensation reactions of oxindole 1 and benzaldehyde derivatives 2 in the presence of piperidine were reported by Wahl and Bagard in 1909 (Scheme 3).12-14
This reaction was also examined under reflux conditions in EtOH in the presence and absence of piperidine.15-17
Scheme 3 Many years later, in 1998, aldehydes and ketones were condensed with oxindole 1 in the presence of KF-Al2O3 and under microwave irradiation, forming good yields of products (81-94%) (Scheme 4). These condensation products 4 and 5 are useful for their biological properties and they can be used as synthons in organic synthesis.18
Scheme 4
In 2012, Mohammadi Ziarani and coworkers performed condensation reaction of oxindole 1 with benzaldehyde derivatives 2 in the presence of sulfonic acid functionalized nanoporous silica (SBA-Pr-SO3H) under solvent-free condition to generate E-isomer of compound 3 (Scheme 5).19
In a related study, compounds 3 were synthesized by condensation of oxindole 1 with several aromatic aldehydes 2. Subsequent asymmetric 1,3-dipolar cycloaddition reaction was carried out by
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