In homogeneous catalysis, the catalyst is in the same phase as the reactant. The number of collisions between reactants and catalyst is at a maximum.In a patent, 2213-63-0, name is 2,3-Dichloroquinoxaline, introducing its new discovery. Quality Control of 2,3-Dichloroquinoxaline
Phosphonylation of 2-amino- and 2-amido-3-bromopyridines and 2-amino-3-chloroquinoxalines with triethyl phosphite
The Tavs reaction of 2-amino- and 2-acylamido-3-bromopyr-idines 1 and 2 with triethyl phosphite in the presence of palladium, acetate or chloride allows the synthesis of 2-aminoand 2-acylamidopyridine-3-phosphonates 3 and 4. A second ring nitrogen atom causes strong activation and leads to excellent yields in the phosphonylation of 2-amino-3-chloroquinoxalines, 2,3-Dichloroquinoxaline does not need a catalyst and undergoes double phosphonylation with sodium diethyl phosphite under Michaelis-Becker conditions. The results show an activating influence of pyridine nitrogen (-M) and deactivating influence of the amino group (+M). The reactivity of 1 and 2 in the Tavs coupling is compared with that of the 3-NH-2-brom.opyridine position isomers and 2-bromo-anilines and discussed in terms of the opposite effects of pyridine and amino(amido) nitrogen and different position of the N atoms towards the reaction site. The advantage of the Tavs reaction is the easy optimization because neither auxiliary ligands are required nor a base to trap the halide or a solvent. Triethyl phosphite itself acts as ligand and forms Pd0[P-(OEt) 3}n in the initial phase of the reaction. The structures of the products and the expected, intramolecular N-H…O=P hydrogen bridging bonds were proven by solution NMR and by X-ray crystal structure analysis of single crystalline 3c. Wiley-VCH Verlag GmbH & Co. KGaA.
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Reference£º
Quinoxaline – Wikipedia,
Quinoxaline | C8H6N1237 | ChemSpider