01258nas a2200133   4500008004100000245009500041210006900136260000800205300001400213520073400227100002200961700002200983856011901005       2017                        eng d00aMethod for the analysis of free carbenes present after NHC-organocatalyzed transformations0 aMethod for the analysis of free carbenes present after NHCorgano  cAUG  a4500-45063 aIn N-heterocyclic carbene (NHC) based organocatalysis, usually, the free carbene is generated in situ by treatment of the azolium salt with a base. Described herein is a method for the analysis of the NHC present in the reaction flask after the NHC-organocatalyzed reaction. For this, the reaction mixture was treated with elemental sulfur after the reaction and the thus-formed thiourea/thione derivative was isolated. Common NHC-catalyzed transformations such as benzoin reactions, Stetter reactions, homoenolate annulation reactions, and reactions proceeding via the ,-unsaturated acylazolium intermediate have been studied. The results indicate that after the reactions, 28-84% of the initial carbenes exist in the free form.1 aDas, Tamal, Kanti1 aBiju, Akkattu, T.  uhttps://library.ncl.res.in/content/method-analysis-free-carbenes-present-after-nhc-organocatalyzed-transformations