Novel catalytic system: N-hydroxyphthalimide/hydrotalcite-like compounds catalysing allylic carbonylation of cyclic olefins

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Date: July 2016
From: Chemical Papers(Vol. 70, Issue 7)
Publisher: Springer
Document Type: Report
Length: 4,879 words
Lexile Measure: 1440L

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N-hydroxyphthalimide (NHPI) combined with stable and recoverable transition metal-aluminium binary hydrotalcite-like compounds (M-Al HTLcs, M = Cu, Ni, Co) as an unprecedented catalytic system was demonstrated for the allylic carbonylation, as the model reaction, of cyclic olefins with tert-butyl hydroperoxide (TBHP), using isophorone (IP) to ketoisophorone (KIP). The results showed NHPI combined with Cu-Al HTLcs to be an efficient catalytic system and the influences of various reaction conditions of the catalytic reaction were optimised. A maximum IP conversion of 68.0 % with 81.8 % selectivity to KIP was afforded under the optimal reaction conditions. Experiments of repeatability and restorability showed Cu-Al HTLcs to be stable for at least five cycles without noticeable loss of catalytic activity. Expanding substrates could also be efficiently converted to the corresponding ketones under the optimised reaction conditions with appreciable yields. A plausible catalytic reaction mechanism was proposed.

[c] 2016 Institute of Chemistry, Slovak Academy of Sciences

Keywords: allylic carbonylation, isophorone, hydrotalcite-like compounds, N-hydroxyphthalimide, tert-butylhydroperoxide

Introduction

In recent decades, the direct and selective allylic carbonylation of cyclic olefins to the corresponding [alpha],[beta]-enones, such as isophorone (IP) to ketoisophorone (KIP), has been investigated for the extensive application of this functional transformation in organic synthesis and industrial chemistry (Chen et al., 2014; Gao et al., 2015; Skobelev et al., 2013), which can substantially simplify reaction procedure and reduce energy consumption; it also results in less pollution than the traditional transformation schemes including the multi-step reaction (Wang et al., 2010; Zalomaeva et al., 2009). However, no general synthetic methodology is readily available due to the unsatisfactory conversion or selectivity and rigorous reaction conditions (Liu et al., 2010; Qiao et al., 2014; Zhou & Tang, 2005). At present, the development of "green", simple, benign, and recyclable catalysts to functionalise the C--H bonds of hydrocarbons with satisfactory conversion and selectivity under moderate conditions is one of the most interesting areas in the field of allylic oxidation (Nakamura & Nakada, 2013; Yang et al., 2009).

N-hydroxyphthalimide (NHPI) and its derivatives have been identified as extraordinary catalysts for the redox reaction of various hydrocarbons via hydrogen abstraction by intermediate phthalimide-N-oxyl (PINO) radical (Chen et al., 2015; Liu et al., 2009; Orlinska, 2010; Wang et al., 2005). However, co-catalysts are required as promoters for achieving the PINO radicals through the precursors NHPI due to its low activity in allylic oxidation (Wang et al., 2010; Yang et al., 2009; Yao et al., 2009). Yang and co-workers (Yang et al., 2005) employed an anthraquinones/NHPI-catalysed system, in which different alkenes were readily oxidised to the desired ketones. Unfortunately, this homogeneous catalytic system for the oxidation of substrates suffers from the drawback of being unrecoverable. Yang et al. (2008) reported ZSM-5-supported metal ions/NHPI and Rajabi and co-workers (Rajabi et al., 2011) employed a silica-supported cobalt salen complex/NHPI as a heterogeneous catalytic system for allylic/benzyl oxidation by improving the Ishii system to circumvent contamination of the products with a transition metal. Although these investigations reported promising results, limitations such as low yield and complicated catalyst render them unacceptable for...

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Gale Document Number: GALE|A462541947