Copper nanoparticles as inexpensive and efficient catalyst: A valuable contribution in organic synthesis

Dihydropyridine (DHP) is among the most beneficial scaffolds that have revolutionised pharmaceutical research with unprecedented biological properties. Over the years, metamorphosis of easily accessible 1,2- and 1,4-dihydropyridine (1,4-DHP) intermediates by synthetic chemists has generated several drug molecules and natural products such as alkaloids. The 1,4-dihydropyridine (1,4-DHP) moiety itself is the main fulcrum of several approved drugs. The present review aims to collate the literature of 1,2- and the 1,4-DHPs relevant to synthetic and medicinal chemists. We will describe various methodologies that have been used for the synthesis of this class of compounds, including the strategies which can furnish enantiopure DHPs, either by asymmetric synthesis or by chiral resolution. We will also elaborate the significance of DHPs towards the synthesis of natural products of medicinal merit.

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Synthesis, utility and medicinal importance of 1,2- & 1,4-dihydropyridines

Molecular Diversity of Three‐Component Reactions of Aromatic Aldehydes, Arylamines, and Acetylenedicarboxylates

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.

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Base Metal Catalyzed Isocyanide Insertions

Organic synthetic reactions mediated by tertiary phosphines have attracted much attention in the organic chemistry community in the past two decades. These reactions can be divided into two categories: phosphine-catalyzed and stoichiometric phosphine-mediated transformations. While the phosphine-catalyzed reactions mechanistically rely on the unique properties of tertiary phosphines such as excellent nucleophilicity and good leaving group ability, the stoichiometric transformations are usually driven by nucleophilicity and strong oxyphilicity of tertiary phosphines. Since tertiary phosphines represent an important class of versatile chemical reagents in organic synthesis, stoichiometric phosphine-mediated reactions have recently demonstrated their uniqueness and high efficiency in organic synthesis, particularly with respect to the construction of carbon–carbon and carbon–heteroatom bonds, and therefore have stimulated much research interest. In this review, recent advances in stoichiometric phosphine-mediated reactions primarily including olefinations and annulations are summarized.

Recent advances in stoichiometric phosphine-mediated organic synthetic reactions

One-pot synthesis of highly functionalized 1,2-dihydropyridines from primary alkylamines, alkyl isocyanides, and acetylenic esters

An efficient synthesis of alkyl 8-hydroxy-6,10-di-oxo-6,10-dihydro-5 H-pyrido[1,2- A]quinoxaline-7-carboxylatesand alkyl 8-hydroxy-6,10-dioxo-6,10-dihydropyrido[2,1- C][1,4]benzoxa-zine-7-carboxylatesis described. This involves the reaction between malonyl dichlorideand alkyl 2-[3,4-dihydro-3-oxo-quinoxaline 2(1 H)-ylidene]acetates or alkyl2-(2-oxo-2 H-benzo[ B][1,4]oxazin-3(4 H)-ylidene)acetates in CH 2 Cl 2 atroom temperature.

An Efficient Synthesis of Functionalized6,10-Dioxo-6,10-dihydro-5H-pyrido[1,2-a]quinoxalines and 6,10-Dioxo-6,10-dihydropyrido[2,1-c][1,4]benz­oxazines

Mohammad J. Bayat

Papers

One-pot synthesis of highly functionalized 1,2-dihydropyridines from primary alkylamines, alkyl isocyanides, and acetylenic esters

An Efficient Synthesis of Functionalized6,10-Dioxo-6,10-dihydro-5H-pyrido[1,2-a]quinoxalines and 6,10-Dioxo-6,10-dihydropyrido[2,1-c][1,4]benzoxazines

Synthesis of amides via copper-catalyzed amidation of aryl halides using isocyanides

Synthesis of N-alkyl-N′-aryl-piperazines via copper-catalyzed C–N bond formation

An efficient organocatalytic method for tandem synthesis of functionalized 2-pyridones

Mohammad J. Bayat

Papers

One-pot synthesis of highly functionalized 1,2-dihydropyridines from primary alkylamines, alkyl isocyanides, and acetylenic esters

An Efficient Synthesis of Functionalized6,10-Dioxo-6,10-dihydro-5H-pyrido[1,2-a]quinoxalines and 6,10-Dioxo-6,10-dihydropyrido[2,1-c][1,4]benz­oxazines

Synthesis of amides via copper-catalyzed amidation of aryl halides using isocyanides

Synthesis of N-alkyl-N′-aryl-piperazines via copper-catalyzed C–N bond formation

An efficient organocatalytic method for tandem synthesis of functionalized 2-pyridones

An Efficient Synthesis of Functionalized6,10-Dioxo-6,10-dihydro-5H-pyrido[1,2-a]quinoxalines and 6,10-Dioxo-6,10-dihydropyrido[2,1-c][1,4]benzoxazines