Inverting the Diastereoselectivity of the Mukaiyama–Michael Addition with Graphite-Based Catalysts

Abstract

Here, we show that graphite-based catalysts, mainly graphite oxide (GO) and exfoliated GO, are effective recyclable catalysts for a relevant stereoselective Mukaiyama− Michael addition, outperforming currently available catalysts. Moreover, the graphite-based catalysts described here invert the diastereoselectivity relative to that observed with known catalysts, with the unprecedented large prevalence of the anti diastereoisomer. This inverted diastereoselectivity is increased when the catalyst concentration is reduced and after catalyst recycling. Density functional theory calculations suggest that the selectivity is determined by two types of supramolecular interactions operating between the catalyst and the substrates at the diastereoselectivity-determining transition state, specifically, the π-stacking of β-nitrostyrene with graphite and the van der Waals interaction between the SiMe 3 group of the silyl ether and the graphite.

Carbon-catalysed reductive hydrogen atom transfer reactions

“…Therefore, the catalytic activity was not derived from metal contamination. When other carbon materials, such as commercially available multi-wall carbon nanotubes, graphene, graphite and activated carbon, were employed in the reaction, the results were less desirable than that obtained using C-0 as a catalyst (entries [25][26][27][28][29]. Therefore, the catalytic activity of our catalyst is unique for the alcohol amination reactions.…”

“…The FT-IR adsorption peaks of multiwall carbon nanotubes, graphene, graphite and activated carbon were weak at 1,570 cm À 1 , which might explain their low activities ( Supplementary Fig. 2 and Table 1, entries [25][26][27][28][29]. It should be mentioned that a high surface area may be important to achieve high activity as well.…”

“…These reactions encompass the oxidative hydrogen atom transfer reactions. In addition, the O-rich carbon materials have been active catalysts in various reactions (that is, nucleophilic addition of alcohol to an epoxide 22 , aldehyde acetalization or esterification 23,24 , Michael addition reactions 25,26 , F-C addition of indoles to a,bunsaturated ketones 27 and synthesis of dipyrromethane 28 , among others 29,30 ). In these studies, nearly all of the organic transformations have been focused on oxidative hydrogen atom transfer reactions or acid-catalysed reactions with heteroatommodified carbon materials (Fig.…”

Graphite oxide as catalyst for diastereoselective Mukaiyama aldol reaction of 2-(trimethylsilyloxy)furan in solvent free conditions

“…some important organic reactions such as Friedel.Crafts, [1,2] oxidations, [3] reductions, [4] Mukaiyama-Michael reaction, [5] this field is still beginning to emerge. The availability, the convenient price and the high sustainability of graphite oxide, make it the right choice to project and build a new way for doing organic chemistry.…”

“…In our previous paper [5] the ability of exfoliated graphene oxide (eGO) to efficiently promote the Mukaiyama -Michael reaction of 2-(trimethylsilyloxy)furan to nitroalkenes was demonstrated with an unprecedent diastereoselective control in favor of anti diastereoisomer with 0.02 wt% of catalyst loading.…”