Annulations involving 1-indanones to access fused- and spiro frameworks.

Indanones are prominent motifs found in number of natural products and pharmaceuticals. Particularly, 1-indanones occupy important niche in chemical landscape due to their easy accessibility and versatile reactivity. In the past few years, significant advancement has been achieved regarding cyclization of 1-indanone core. The present review focuses on recent (2016-2022) annulations involving 1-indanones for the construction of fused- and spirocyclic frameworks. In this context, new strategies for synthesis of various carbocyclic as well as heterocyclic skeletons are demonstrated. Mechanistic aspects of representative reactions are illustrated for better understanding of reaction pathways. A large number of transformations described in this review offer stereoselective formation of desired polycyclic compounds. Importantly, several reactions provide biologically relevant compounds and natural products, such as, plecarpenene/plecarpenone, swinhoeisterol A, cephanolides A-D, diptoindonesin G and atlanticone C.

Stereoselective synthesis of fused-, spiro- and bridged heterocycles via cyclization of isoquinolinium salts: a recent update.

Isoquinoline and its derivatives are ubiquitous in natural alkaloids, synthetic materials and pharmaceuticals with a broad spectrum of biological activities. In particular, isoquinolinium salts are important in organic synthesis because they can serve as building blocks for the rapid construction of various condensed heterocyclic systems involving cyclization processes. This review highlights novel stereoselective strategies that emerged in the last few years (2014-2021) for the synthesis of various fused-, spiro- and bridged heterocycles exploiting bench-stable or in situ generated isoquinolinium salts. Most of the reactions described here provide quick access to the desired products with high stereoselectivity starting from readily available starting materials under mild conditions. The synthetic potential of most of the transformations was confirmed by the gram-scale production of the target molecules. Some of the reactions have been useful for the synthesis of natural products and other bioactive compounds.

Recent applications of ninhydrin in multicomponent reactions.

Ninhydrin (1,2,3-indanetrione hydrate) has a remarkable breadth in different fields, including organic chemistry, biochemistry, analytical chemistry and the forensic sciences. For the past several years, it has been considered an important building block in organic synthesis. Therefore, there is increasing interest in ninhydrin-based multicomponent reactions to rapidly build versatile scaffolds. Most of the works described here are simple reactions with readily available starting materials that result in complex molecular architectures. Some of the synthesized compounds exhibit interesting biological activities and constitute a new hope for anticancer agents. The present review aims to highlight the multicomponent reactions of ninhydrin towards diverse organic molecules during the period from 2014 to 2019.

Synthesis and fluorescent properties of a new class of heterocycles of isoindole fused imidazoles with phenolic subunits.

A new class of heterocycles of isoindole fused imidazoles with phenolic subunits has been readily synthesized by a two-step one-pot reaction. In aprotic solvent they show high fluorescent properties (Phi(F) up to 0.93), but in protic polar solvent fluorescent intensity decreases. They show green fluorescence in weak acidic medium such as acetic acid but lack emission in basic medium. The compounds can also stain human squamous epithelium cells.