Current Organic Chemistry - Volume 23, Issue 8, 2019

N-Heterocyclic compounds like 1,2,3-triazoles serve as a key scaffolds among organic compounds having diverse applications in the field of drug discovery, bioconjugation, material science, liquid crystals, pharmaceutical chemistry and solid phase organic synthesis. Various drugs containing 1,2,3-triazole ring which are commonly available in market includes Rufinamide, Cefatrizine, Tazobactam etc., Stability to acidic/basic hydrolysis along with significant dipole moment support triazole moiety for appreciable participation in hydrogen bonding and dipole-dipole interactions with biological targets. Huisgen 1,3-dipolar azide-alkyne cycloaddition culminate into a mixture of 1,4 and 1,5- disubstituted 1,2,3-triazoles. In 2001, Sharpless and Meldal came across with a copper(I) catalyzed regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles by cycloaddition between azides and terminal alkynes. This azide-alkyne cycloaddition has been labelled as a one of the important key click reaction. Click synthesis describes chemical reactions that are simple to perform, gives high selectivity, wide in scope, fast reaction rate and high yields. Click reactions are not single specific reaction, but serve as a pathway for construction of simple to complex molecules from a variety of starting materials. In the last few decades, 1,2,3-triazoles attracted attention of researchers all over the world because of their broad spectrum of biological activities. Keeping in view the biological importance of 1,2,3-triazole, in this review we focus on the various synthetic routes for the syntheisis of 1,4-disubstituted 1,2,3-triazoles. This review involves various synthetic protocols which involves copper and non-copper catalysts, different solvents as well as substrates. It will boost synthetic chemists to explore new pathway for the development of newer biologically active 1,2,3-triazoles.

Amide bonds are amongst the most fundamental groups in organic synthesis, and they are widely found in natural products, pharmaceuticals and material science. Over the past decade, methods for the direct amination of aldehydes have received much attention as they represent atom- and step-economic routes for amide synthesis from readily available starting materials. Herein, the research advances on the direct amination of aldehydes are reviewed and categorized by the types of catalyst system. Detailed reaction scopes and mechanisms will be discussed, as well as the limitations of current procedures and the prospects for the future.

In recent years, the synthesis of quinoline scaffold using various methodological devices has attracted considerable attention in synthetic chemist community. The most feasible method to serve this purpose is Aza-Diels-Alder reaction which provides flexibility and diversity in the synthesis of quinoline decorated with different functionalities over the scaffold. Diversity in this functionality improvises the susceptibility of the quinoline scaffold for various protein targets. This review encompasses multifactorial aspects of Aza-Diels-Alder reaction as well as provides insights into the synthetic schemes for quinoline scaffold.

10-Aminovindoline and 17-desacetylvindoline were coupled with 5α- dihydrotestosterone hemisuccinate and 19-nortestosterone hemisuccinate. As a result, four vindoline-steroid hybrids were synthesized via a succinate linker. One of the new hybrid compounds showed significant anticancer effect in vitro in the case of colon cancer and melanoma cell lines.

The addition of phosphorous acid on the C=O group of substituted benzaldehydes in the presence of hydrochloric acid in water affords a mixture of the corresponding α - chlorophosphonic acid and α-hydroxyphosphonic acid. The selectivity towards the α-chloro derivatives may be increased to 92% by the excess of HCl applying forcing conditions. α- Hydroxyphosphonic acids may be synthesized better in yields of 83-92% by the hydrolysis of the corresponding dimethyl α-hydroxyphosphonates. α-Chlorophosphonic acids may also be obtained in yields of 66-79% from α -hydroxyphosphonic esters by reaction with thionyl chloride followed by hydrolysis. The α -chlorophosphonic acids and esters are useful intermediates for other phosphonic derivatives.