Current Organic Chemistry - Volume 24, Issue 10, 2020

Pyrimidine heterocycles are proven to be biologically active heterocycles, found in many biological systems, displaying a broad spectrum of biological activities including anticancer, anxiolytic, antioxidant, antiviral, antifungal, anticonvulsant, antidepressant and antibacterial activities. Recently, various synthetic approaches, synthetic strategy, the variation of substrates and study devoted towards the evaluation of biological activities for the pyrimidine heterocycles have been reported in the literature. This review article describes the synthesis of various biologically interesting pyrimidine heterocyclic ring systems using various nitrogen building blocks.

Boron possesses the second greatest heating value of any element that can be adopted as an energetic material in the processing of propellants and explosives. It has become the first choice as a high energy fuel for solid fuel-rich propellants because of its advantages of high theoretical combustion heat. In the actual condition, the combustion efficiency of boron-containing fuel-rich propellants is low, and the potential energy of boron cannot be fully utilized. The compound containing-boron can be used as a new way to improve the combustion efficiency of fuel-rich propellants. In this paper, the progress in the synthesis of energetic borides is reviewed from the perspectives of molecular design, synthesis strategy and route optimization. The situation of the synthesis methods of energetic borides (nitrogen-rich boron esters, poly(azole)borates, nitroboranes, nitrogen-rich borazines and azide boron compounds) is reviewed. The research focus and development trend of various boron compounds are analyzed, and the potential application prospect in the propellant is investigated.

Quinazoline is an organic heterocyclic molecule in which two six-membered aromatic rings are fused. Two nitrogen atoms are present in the quinazoline molecule at 1 and 3 positions that is why it is also known as 1,3-diazanaphthalene. The presence of these two nitrogen atoms in 1,3-diazanaphthalene increases the usefulness of this molecule in the field of pharmaceutical sciences. Many reactions have been reported to prepare 1,3- diazanaphthalene by aminobenzonitrile, o-aminobenzohydrazide, aminobenzamide, aminoacetophenone, and aminobenzoketone under different solvent conditions, but condensation of anthranilic acid with an aromatic aldehyde is the most common method. Later, metal-free and solvent-free conditions dominated over the old methods. This review describes the synthesis of 1,3-diazanaphthalene under different metal catalysts, reagents, solvent- free conditions and under microwave radiation through nucleophilic substitution reaction, condensation, and aromatization. In biological sciences, 1,3-diazanaphthalene derivatives have got an important place due to their ability to bind to different target sites and subsequent discovery of many drug structures.

2-Phenylcyclododecanone and 2-cyclohexylcyclododecanone derivatives were synthesized and characterized by 1H NMR, 13C NMR, HR-ESI-MS and X-ray diffraction. Their preferred conformations were analyzed by the coupling constants in the 1H NMR spectra and X-ray diffraction, which showed the skeleton ring of these derivatives containing [3333]-2-one conformation, and the phenyl groups were located at the side-exo position of [3333]-2-one conformation due to the strong π-π repulsive interaction between the π- electron of benzene ring and π-electron of carbonyl group. The cyclohexyl groups were located at the corner-syn or the side-exo position of [3333]-2-one conformation depending on the hindrance of the other substituted groups. The π-π electron effect played a crucial role in efficiently controlling the preferred conformation of 2-aromatic cyclododecanone and the other 2-aromatic macrocyclic derivatives with the similar preferred square and rectangular conformations.

Carbon centered molecules have been very well recognized in the past for both academic and industrial purposes. Utilizing inert element instead of carbon atom could bring more molecular complexity as well as potential binding in medicinal chemistry. We report, herein, a number of strategies for the syntheses of Ru-centered molecules starting from commercially available [RuCl2(η6-p-cymene)] dimer substituted phenyl-heterocycles via Concerted Metalation Deprotonation (CMD) processes. Halogen atom ligand exchange and arene ligand exchange from the skeleton have been achieved. Under such procedures, a collectively good number of (26) Ru-arene complexes have been prepared efficiently. The Ru-complexes prepared have covered broad spectrum of functional groups on the 4 possible positions. Moreover, the Suzuki coupling reaction on the Ru-centered complex was realized with good yield (90%). The access of a library of these compounds would allow molecular chemists to consider the utilization of these molecules rather than purely organometallic reagents for inorganic chemistry or catalysis.