Put it on a ring: A rhodium(III) complex can catalyze the oxidative coupling of azomethine imines with olefins, leading to the synthesis of 1,2‐dihydrophthalazines, olefinated aldehydes, or fused pyridines, depending on the conditions used.
The rhodium(III)‐catalyzed coupling of azomethine ylides with alkynes via CH activation has been developed for the synthesis of indenamines in moderate to high yields. The coupled products can be further oxidized to indenones and derivatives.
AgOTf can catalyze an addition-cyclization tandem between alkyne-azomethine and a nucleophile such as ketone, nitroalkane, water, and terminal alkyne to give a polycyclic amide via six-exo-trig selectivity.Alkynes are widely used in synthetic chemistry and it has been well documented that, upon coordination to metals such as Au(I), Au(III), Pt(II), Pd(II), Ag(I) and I(I), alkynes are susceptible to nucleophilic attack, leading to cyclization reactions.1 Such a metal-induced process has played an important role in the synthesis of complex synthetic targets. Compared to the vast majority of gold-catalyzed heterocyclization of alkynes, related Ag(I)-catalyzed reactions are less common, although silver catalysts are generally more cost-effective and can offer complementary reactivity and higher functional group compatibility.1i,j,2 When an ortho alkyne-functionalized aldehyde was applied as a substrate in the presence of an external nucleophile (NuH) such as an alcohol, nucleophilic addition of the aldehyde to alkyne can trigger a further addition of the NuH to the carbonyl group, giving rise to cyclization with additional functionalization. 2f,3 Despite the success, this type of reactivity has been mostly observed for alkyne-tethered carbonyl compounds and in most cases endo cyclization selectivity was followed.2k Thus alkyne-functionalizaed imines have been less explored. 4 In order to further explore and expand the utility of Ag(I) catalysis in cyclization reactions for molecular diversity and complexity, it is necessary to broaden the scope of both the alkyne-imine and the external nucleophile substrates.We recently reported rhodium-catalyzed CÀH activation of azomethine imines derived from arylaldehydes,
Ringe à la carte: Ein Rhodium(III)‐Komplex katalysiert die oxidative Kupplung von Azomethiniminen mit Olefinen. Je nach Reaktionsbedingungen gelingt damit die Synthese von 1,2‐Dihydrophthalazinen, olefinierten Aldehyden oder anellierten Pyridinen.
Rhodium(III)-Catalyzed Annulation of Azomethine Ylides with Alkynes via C-H Activation. -A wide range of different substituted substrates can be used for the title reaction. The products can be further oxidized to indenones or derivatives, e.g. (X) and (XI). -(CHEN, Y.; WANG, F.; ZHEN, W.; LI*, X.; Adv. Synth. Catal. 355 (2013) 2-3, 353-359, http://dx.
Rhodium(III)-Catalyzed Oxidative C-H Functionalization of Azomethine Ylides. -Depending on the conditions A) or B) mono-and diolefinated dihydrophthalazines such as (III) and (IV) are generated. Starting from azomethin functionalized with a heteroaromatic compound pyridine-fused heterocycles (X) and (XII) arise. Switching the oxidant to a copper salt induces ortho-olefinated heteroarylaldehydes. -(ZHEN, W.; WANG, F.; ZHAO, M.; DU, Z.; LI*, X.; Angew. Chem., Int. Ed. 51 (2012) 47, 11819-11823, http://dx.
The new method presented here is applicable to various nucleophiles such as ketones, nitroalkanes, and terminal alkynes giving a number of polycyclic amides.
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