Pyrazines. 1_re communication. I. Synthèse de méthyl‐2‐pyrazines alcoylées en 3, par condensation de l'éthylènediamine avec les dioxo‐2,3‐alcanes

Abstract

The synthesis of eight 2‐methyl 3‐alkyl pyrazines by catalytic dehydrogenation of condensation products of ethylenediamine with 2,3‐diketoalkanes is described.

Iodine(V) Reagents in Organic Synthesis. Part 2. Access to Complex Molecular Architectures via Dess−Martin Periodinane-Generated o-Imidoquinones

“…Given their importance in medicinal chemistry, we then turned our attention to the synthesis of pyrazines as seen in Scheme ( 42 → 55d ). In an expanded venture and as shown in Table , the combination of ketohydroxyamide 42 with a variety of 1,2-diamines led smoothly to complex polycyclic pyrazines, presumably via a straightforward condensation with the intermediately formed diketone (e.g., 50 , Scheme ) . Because of the high efficiency of these reactions, we proceeded to employ C-protected amino acids as coupling partners and discovered an interesting cascade sequence leading to heterocyclic annulation as shown in Scheme ( 42 → 56a ).…”

Polystyrene bound oxidovanadium(IV) and dioxidovanadium(V) complexes of histamine derived ligand for the oxidation of methyl phenyl sulfide, diphenyl sulfide and benzoin

“…The selective oxidation of a-hydroxyketones to a-diketones is one of the important reactions in fine chemical synthesis. [31][32][33][34][35] The oxidation of benzoin has attracted the attention of researchers because one of its oxidised products, benzil, is a very useful intermediate for the synthesis of heterocyclic compounds and benzylic acid rearrangements. 36 Here, the oxidation of benzoin was successfully achieved with the catalyst PS-[V V O 2 (sal-his)] 2 using 30% aqueous H 2 O 2 as oxidant.…”

Solvent Effect on the Sensitized Photooxygenation of 2,3-Dihydropyrazine Derivatives

“…5,6-Dimethyl-2,3-dihydropyrazine (DMD) and 5-methyl-6-phenyl-2,3-dihydropyrazine (MPD) were synthesized as described; typically a solution of 1-phenyl-2-propanedione (5 g) in ethyl ether (10 mL) was added to ethylendiamine (2 g) in 10 mL of ethyl ether maintained at 0 °C. The mixture was refluxed for 30 min and the ethereal yellow solution was dried over sodium sulfate and the solvent removed in a vacuum.…”