Tris-ureas as versatile and highly efficient organocatalysts for Michael addition reactions of nitro-olefins: mechanistic insight from in-situ diagnostics

Bera, Milan ; Ghosh, Tamal Kanti ; Akhuli, Bidyut ; Ghosh, Pradyut (2015) Tris-ureas as versatile and highly efficient organocatalysts for Michael addition reactions of nitro-olefins: mechanistic insight from in-situ diagnostics Journal of Molecular Catalysis A: Chemical, 408 . pp. 287-295. ISSN 1381-1169

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Official URL: http://www.sciencedirect.com/science/article/pii/S...

Related URL: http://dx.doi.org/10.1016/j.molcata.2015.01.004

Abstract

Tris(2-aminoethyl)-amine, TREN based tris-ureas (1a–1d) and tris-thiourea (1e) have been explored towards a wide range of catalytic Michael addition reactions. These tris-ureas, 1a–1d efficiently catalyze the addition reaction of β-nitro styrenes (2a–2d) with various nucleophiles such as β-ketoesters (3a–3c), 1,3-dicarbonyl compound (3d), a cyanoester (3e) and a nitroester (3f) under ambient conditions to produce corresponding nitro alkanes in high yields. Pentafluorophenyl attached tris-urea, 1d is found to be the most effective catalyst in the series that yields 78–98% products conversion. In case of the reaction between β-nitro styrenes and malononitrile (3g) in presence of 1d, 2-amino-5-nitro-4,6-diphenylcyclohex-1-ene-1,3,3-tricarbonitriles are also isolated as a minor product along with the corresponding Michael adduct. The added advantage of bridge-head nitrogen center in tris-urea organocatalysts, 1a–1d has been established by studying analogous benzene platform based tris-ureas (1f, 1g, 1h) in similar experimental conditions. Furthermore, a plausible reaction mechanism has also been established based on in-situ 1H NMR kinetic studies.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Michael Addition Reaction; Tris-urea Catalyst; Organocatalysis; Hammett Plot
ID Code:102703
Deposited On:23 Jan 2017 06:41
Last Modified:23 Jan 2017 06:43

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