Correction: Insights into the unexpected chemoselectivity in Brønsted acid catalyzed cyclization of isatins with enaminones: convenient synthesis of pyrrolo[3,4-c]quinolin-1-ones and spirooxindoles

Abstract

Correction for ‘Insights into the unexpected chemoselectivity in Brønsted acid catalyzed cyclization of isatins with enaminones: convenient synthesis of pyrrolo[3,4-c]quinolin-1-ones and spirooxindoles’ by Hui Xu et al., Chem. Commun., 2016, 52, 8002–8005.

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The authors regret that in the original article the structures of some compounds in Table 2, Scheme 2 and Scheme 4 were reported incorrectly. Please see below for a detailed breakdown of these errors and the relevant corrections.

In Table 2, the identity of the R³ substituent on compounds 3da, 3db, 3dc, 3dd, 3de is listed incorrectly. A corrected version of Table 2, with the changes highlighted in red text, is presented herein.

Table 1 Substrate scope of 3-acyloxy-pyrroloquinolines 3^a,b

a Isolated yields. b For the optimization of the solvent, reaction temperature and stoichiometry for reactions of propanoic acid and benzoic acid, see Tables S3 and S4 in the ESI.

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In Scheme 2, the identities of the R¹, R² and R³ substituents in reaction schemes (a) and (b) are presented incorrectly. A corrected version of Scheme 2, with the changes highlighted in red text, is presented herein. These errors also affect the sentence on page 8004 beginning “Moreover, methoxylated product 3eh…”, which should now read “Moreover, methoxylated product 3eh instead of hydroxylated 3ej was obtained in the presence of TFA (10 mol%) and MeOH (Scheme 2b).”

Scheme 2 Studies on the source of the hydroxyl group, and the substrate scope of 3-hydroxy-pyrroloquinolines 3; reaction conditions: 1 (0.5 mmol) and 2 (0.5 mmol). A: 1,4-dioxane (2.0 mL), TFA (10.0 equiv.), 110 °C, 2 h; F: DCM (2.0 mL), TFA (5.0 equiv.), r.t.; G: DCM (dry, 2.0 mL), 4 Å M.S., TFA (5.0 equiv.), r.t.; H: DCM (1.0 mL), water (1.0 mL), TFA (5.0 equiv.), r.t.; I: DCM (dry, 2.0 mL), 4 Å M.S., CF₃SO₃H (5.0 equiv.), r.t.; J: DCM (dry, 2.0 mL), 4 Å M.S., HCOOH (5.0 equiv.), r.t.; K: DCM (dry, 2.0 mL), 4 Å M.S., p-TSA (5.0 equiv.), r.t.

In Scheme 4, the compound reference numbers used to describe the products in reaction schemes (c)–(i) are incorrect. A corrected version of Scheme 4, with the changes highlighted in red text, is presented herein. These errors do not affect the original characterisation in the ESI, in which the correct compound reference numbers are used. However, the corresponding main article text is affected. On page 8004, in the paragraph beginning “To understand the nature of the novel catalyst-controlled…”, citations to compounds 4m–q should be changed to citations to compounds 4p–t, respectively.

Scheme 4 Control experiments.

The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.

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