Isocyanides are diverse C1 building blocks considering their potential to react with nucleophiles, electrophiles, and radicals. Therefore, perhaps not surprisingly, isocyanides are highly valuable as inputs for multicomponent reactions (MCRs) and other one‐pot cascade processes. In the field of organometallic chemistry, isocyanides typically serve as ligands for transition metals. The coordination of isocyanides to metal centers alters the electronic distribution of the isocyano moiety, and reaction pathways can therefore be accessed that are not possible in the absence of the metal. The tunable reactivity of the isocyanide functional group by transition metals has evolved into numerous useful applications. Especially palladium‐catalyzed isocyanide insertion processes have emerged as powerful reactions in the past decade. However, reports on the use of earth‐abundant and cheap base metals in these types of transformations are scarce and have received far less attention. In this Minireview, we focus on these emerging base metal catalyzed reactions and highlight their potential in synthetic organic chemistry. Although mechanistic studies are still scarce, we discuss distinct proposed catalytic cycles and categorize the literature according to 1) the (hetero)atom bound to and 2) the type of bonding with the transition metal in which the (formal) insertion occurs.
The N-iodosuccinimide-mediated spirocyclization of tryptamine-derived isocyanides to generate spiroindolenines is reported. The products contain both an imine and an imidoyl iodide as flexible handles for follow-up chemistry.N ucleophilic addition typically occurs chemoselectively on the imine moiety with complete diastereoselectivity,p roviding opportunities for the construction of complex molecular frameworks. The synthetic potential of the method was showcased in the formal total synthesis of (AE)-aspidofractinine.
Isocyanides have long been known as versatile chemical reagents in organic synthesis. Their ambivalent nature also allows them to function as a CO-substitute in palladium-catalyzed cross couplings. Over the past decades, isocyanides have emerged as practical and versatile C1 building blocks, whose inherent N-substitution allows for the rapid incorporation of nitrogeneous fragments in a wide variety of products. Recent developments in palladium catalyzed isocyanide insertion reactions have significantly expanded the scope and applicability of these imidoylative cross-couplings. This review highlights the advances made in this field over the past eight years.
Herein,
we report a novel copper-catalyzed imidoylative cross-coupling/cyclocondensation
reaction between 2-isocyanobenzoates and amines efficiently producing
quinazolin-4-ones. The reaction utilizes Cu(II) acetate as an environmentally
benign catalyst in combination with a mild base and proceeds well
in anisole, a recommended, sustainable solvent. Additionally, the
reaction does not require dry conditions or inert atmospheres for
optimal performance. The scope of this isocyanide insertion reaction
is rather broad, tolerating various functionalized isocyanobenzoates
and a range of substituted amines, although the use of aromatic amines
as nucleophiles requires microwave heating.
In this review the transition metal-catalysed carbene- and nitrene transfer to carbon monoxide and isocyanides will be disclosed. The resulting heteroallene allows for in situ transformation towards numerous functional groups and organic compounds.
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