Application of N-heterocyclic carbene-Cu(I) complexes as catalysts in organic synthesis: a review.

N-Heterocyclic carbenes (NHCs) are a special type of carbenes in which the carbene carbon atom is part of the nitrogen heterocyclic ring. Due to the simplicity of their synthesis and the modularity of their stereoelectronic properties, NHCs have unquestionably emerged as one of the most fascinating and well-known species in chemical science. The remarkable stability of NHCs can be attributed to both kinetic as well as thermodynamic effects caused by its structural features.

Dienophilic reactivity of 2-phosphaindolizines: a conceptual DFT investigation.

The >C=P- or -N=P- functionality in 1,3-azaphospholo[1,5-]pyridine, named as 2-phosphaindolizine and its 1- and 3-aza derivatives act as dienophiles and undergo Diels-Alder reactions with 1,3-dienes. However, the dienophilic reactivity is affected by the nature of the substituent groups on the two sides of the σ,λ-P atom and also by the presence of more nitrogen atom(s) in the five-membered ring. The conceptual density functional theory (DFT) calculations have been used in recent years to predict the reactivity of organic molecules in reactions.

A new cross-conjugated mesomeric betaine.

Cross-conjugated mesomeric betaine (CCMB) has been defined as the dipolar species in which positive and negative charges are restricted to different parts of the molecule. In contrast to indolizine which undergoes [8+2] cycloaddition with dimethyl acetylenedicarboxylate (DMAD), its 1-aza analogue, namely imidazo[1,2-]pyridine reacts with the same reagent to afford the first representative of the CCMB isoconjugate with the odd non-alternant hydrocarbon anion. The structure of the product could be assigned on the basis of the NMR and HRMS results.