Pd/C-catalyzed heterocyclization during copper-free Sonogashira coupling: synthesis of 2-benzylimidazo[1,2-a]pyrimidines in water

Recent Advances of Pd/C-Catalyzed Reactions

The Pd/C-catalyzed reactions, including reduction reactions and cross-coupling reactions, play an irreplaceable role in modern organic synthesis. Compared to the homogeneous palladium catalyst system, the heterogeneous Pd/C catalyst system offers an alternative protocol that has particular advantages and applications. Herein, a review on Pd/C-catalyzed reactions is presented. Both the advances in Pd/C-catalyzed methodologies and the application of Pd/C-catalysis in total synthesis are covered in this review.

Diels-Alder versus 1,3-dipolar cycloaddition pathways in the reaction of C20 fullerene and 2-furan nitrile oxide

As one of the smallest carbon cages, C20 and its properties are very important. The nature of these compounds, and the development of procedures for their functionalisation for end-use in nano sized devices, have become important fields. Both Diels–Alder and 1,3-dipolar cycloaddition reactions are appropriate strategies to functionalise carbon nano tubes and C60 fullerenes. In this regard a comparison between two pathways of interaction between C20 and 2-furan nitrile oxide has been performed here to determine which reaction, Diels–Alder or 1,3-dipolar addition, is more suitable for functionalisation of C20. The results showed that 1,3-dipolar cycloaddition is faster than the Diels–Alder reaction for the functionalisation of C20 fullerene by 2-furan nitrile oxide.

A Theoretical Study on the Functionalisation Process of C18NB Fullerene Through its Open [5,5] Cycloaddition with 4-Pyridine Nitrile Oxide

C20 nanofullerene and its derivatives, as the smallest carbon cages, are amongthe most important compounds in the field of nanoscience. As a result, it is very important to find a procedure to functionalise these precious compounds to exploit their numerous benefits. So, in this study, the process was investigated of adding a functional group to one of the C20 fullerene derivatives, via its open [5,5] cycloaddition reaction with 4-pyridine nitrile oxide. This showed that the open [5,5] cycloaddition reaction between 4-pyridine nitrile oxide and C18NB fullerene takes place with sufficient speed that would need no catalyst.

According to the calculations, a highly asynchronous concerted mechanism operates in this reaction. It seems that oxygen–boron interaction causes the mechanism to be asynchronous. All calculations were performed at the B3LYP/6-311G(d,p) level of theory.

Synthetic approaches and functionalizations of imidazo[1,2-a]pyrimidines: an overview of the decade

This review gives an overview to the synthesis of the imidazo[1,2-a]pyrimidines on the basis of multicomponent reactions, condensation reactions, intramolecular cyclizations etc. along with its reactivity at 3-position.

Rapid access to compound libraries through flow technology: fully automated synthesis of a 3-aminoindolizine library via orthogonal diversification

A novel methodology for the synthesis of druglike heterocycle libraries has been developed through the use of flow reactor technology. The strategy employs orthogonal modification of a heterocyclic core, which is generated in situ, and was used to construct both a 25-membered library of druglike 3-aminoindolizines, and selected examples of a 100-member virtual library. This general protocol allows a broad range of acylation, alkylation and sulfonamidation reactions to be performed in conjunction with a tandem Sonogashira coupling/cycloisomerization sequence. All three synthetic steps were conducted under full automation in the flow reactor, with no handling or isolation of intermediates, to afford the desired products in good yields. This fully automated, multistep flow approach opens the way to highly efficient generation of druglike heterocyclic systems as part of a lead discovery strategy or within a lead optimization program.

A DFT Study on the Cycloaddition of Dimethyl Acetylenedicarboxylate and 3,4-dihydroisoquinoline-N-oxide

A theoretical study of the kinetics and mechanism of the second-order intermolecular cycloaddition of dimethyl acetylenedicarboxylate and [3,4-dihydroiso-quinoline-N-oxide] was performed using DFT methods at B3LYP levels of theory with a 6-311G (d,p) basis set at 298.15 K. Equilibrium molecular geometries and harmonic vibrational frequencies of the reactants, transition state and product were calculated. The effect of solvent on the kinetic and thermodynamic parameters of the reaction were investigated. The calculated rate constants and activation parameters showed good agreement with experimental results. These calculations indicated that the reaction proceeds through a synchronous concerted mechanism.