Pd-NHC Catalytic System for the Efficient Atom-Economic Synthesis of Vinyl Sulfides from Tertiary, Secondary, or Primary Thiols

Vinyl sulfides represent an important class of compounds in organic chemistry and materials science. Atom-economic addition of thiols to the triple bond of alkynes provides an excellent opportunity for environmentally friendly processes. We have found that well-known and readily available Pd-NHC complex (IMes)­Pd­(acac)Cl is an efficient catalyst for alkyne hydrothiolation. The reported technique provides a general one-pot approach for the selective preparation of Markovnikov-type vinyl sulfides starting from tertiary, secondary, or primary aliphatic thiols, as well as benzylic and aromatic thiols. In all the studied cases, the products were formed in excellent selectivity and good yields

Diversity Oriented Synthesis of Polycyclic Heterocycles through the Condensation of 2‑Amino[1,2,4]triazolo[1,5‑<i>a</i>]pyrimidines with 1,3-Diketones

The acid-catalyzed condensation between 2-aminosubstituted [1,2,4]­triazolo­[1,5-<i>a</i>]­pyrimidines and their analogues with various saturation of the pyrimidine ring and 1,3-diketones or 1,1,3,3-tetramethoxypropane was evaluated as a new approach for the synthesis of diversely substituted polycyclic derivatives of triazolopyrimidine. The reaction of 4,5,6,7-tetrahydro- or aromatic aminotriazolopyrimidines results in selective formation of the corresponding [1,2,4]­triazolo­[1,5-<i>a</i>:4,3-<i>a</i>′]­dipyrimidin-5-ium salts, and the condensation of substrates containing the 4,7-dihydro-[1,2,4]­triazolo­[1,5-<i>a</i>]­pyrimidine fragment is accompanied by a cascade rearrangement with unusual recyclization of the dihydropyrimidine ring to yield partially hydrogenated [1,2,4]­triazolo­[1,5-<i>a</i>:4,3-<i>a</i>′]­dipyrimidin-5-ium or pyrimido­[1′,2′:1,5]­[1,2,4]­triazolo­[3,4-<i>b</i>]­quinazolin-5-ium salts. The proposed methodology exhibits a wide scope, providing rapid access to polycondensed derivatives of the [1,2,4]­triazolo­[1,5-<i>a</i>]­pyrimidine scaffold. DFT calculations of the Gibbs free energies of possible isomers were performed to rationalize the experimentally observed reactivity and selectivity