Beilstein J. Org. Chem.2017,13, 1564–1571, doi:10.3762/bjoc.13.156
-substituted isoquinolines at C-1, followed by reaction with iodine. Subsequent Suzuki cross-coupling of the resulting 1-iodoisoquinolines to methyl 2-(isoquinolin-1-yl)benzoates and intramolecular acylation of the corresponding carboxylic acids with Eaton’sreagent afforded five alkaloids of the
cytotoxicity against the HL-60 tumor cell line.
Keywords: directed ortho/remote metalation; Eaton’sreagent; isoquinolines; Suzuki cross-coupling; Introduction
Benzylisoquinoline alkaloids represent a very large group of plant secondary metabolites, which includes about 2,500 known structures. Besides simple
reaction conditions. As an alternative reagent for the acylation of arenes with esters Eaton’sreagent (phosphorus pentoxide, 7.7 wt % in methanesulfonic acid) has been described in the literature [28][29]. Eaton’sreagent has advantages over polyphosphoric acid as it is an easy to handle, non-viscous and
Beilstein J. Org. Chem.2012,8, 1849–1857, doi:10.3762/bjoc.8.213
, is described, involving the intramolecular Friedel–Crafts acylation reaction of 2-(phenoxymethyl)-4-phenylquinoline-3-carboxylic acid derivatives 3a–l aided by the treatment with PPA (polyphosphoric acid) or Eaton’sreagent. The required starting compound (2) was obtained by Friedländer reaction of 2
three-step route, offers easy access to tetracyclic-fused quinoline systems in short reaction times, and the products are obtained in moderate to good yields.
Keywords: Eaton’sreagent; Friedel–Crafts acylation; Friedländer reaction; one-pot; PPA; quinoline; tetracyclic-fused; Introduction
Polycyclic
alternative route would be desirable. Recently, the Eaton’sreagent, a mixture of P2O5 and MeSO3H [43], has gained wide application as an advantageous medium for cyclization reactions [44], and we have also reported the serendipitous discovery of its excellent performance in these types of transformations [32
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Graphical Abstract
Scheme 1:
Synthesis of ethyl 2-(chloromethyl)-4-phenylquinoline-3-carboxylate (2).