2 research outputs found
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