N-Heterocyclic carbenes are regarded as neutral compounds containing a divalent carbon atom with a six-electron valence shell, carbenes are an intriguing class of carbon-containing compounds. The successful isolation and characterization of an N-heterocyclic carbene in 1991 opened up a new class of organic compounds for investigation. They are cyclic molecules that contain one carbene and at least one nitrogen atom within the carbene-containing ring structure. These molecules are widely used as ancillary ligands for the preparation of transition-metal-based catalysts and also possess a unique characteristic feature i.e. Umpolung nature. The underlying principle of many of the NHC-catalyzed reactions is the remarkable ability of NHCs to reverse the normal mode of reactivity of aldehydes (umpolung). NHCs can catalyze transformations proceeding via the umpolung or nonumpolung mode for the synthesis of various functionalized molecules.

A simple method for the iodination of unsaturated sugars to form sugar vinyl iodides was developed under oxidantfree conditions using NaH/DMF/iodine as a reagent system at ambient temperature. 2-Iodoglycals bearing ester, ether, silicon, and acetonide protection were synthesized in good to excellent yield. 3-Vinyl iodides derived from 1,2:5,6-diacetonide glucofuranose were transformed to C-3 enofuranose and bicyclic 3,4-pyran-fused furanose via Pd-catalyzed C-3 carbonylation and intramolecular Heck reaction, respectively, as the key step.

Correction for ‘Diastereoselective synthesis of glycopyrans 1,2-annulated with dioxazinanes from 1,2-anhydrosugars and N-substituted nitrones’ by Ajaz Ahmed et al., Org. Biomol. Chem., 2022, 20, 1436–1443, DOI: 10.1039/d1ob02310a.