Ortho-selectivity in SNAr substitutions of 2,4-dihaloaromatic compounds. Reactions with anionic nucleophiles
作者:Michael D. Wendt、Aaron R. Kunzer
DOI:10.1016/j.tetlet.2010.03.124
日期:2010.6
in a variety of solvents. Substrates showed strong preferences for ortho substitution in most cases. Evidence is presented for activating group-dependent coordination, which contributes to very high ortho-selectivity in nonpolar solvents. This also drives the overall reaction rate in these solvents, and is of close to the same magnitude of rate increase derived from polar solvents. para-Products are
Substituted N-aryl[1,2,4]triazolo[1,5-a]pyridine-2-sulfonamide compounds, such as N-(2,6-difluorophenyl)-5-methoxy-7-methyl[1,2,4]triazolo[1,5-a]pyridine-2- sulfonamide, N-(4-bromo-1-methyl-3-pyrazoly)-8-chloro-5-methoxy[1,2,4]triazolo[1,5-a]py ridine-2-sulfonamide, and N-(2-fluoro-4-methyl-3-pyridinyl)-8-ethoxy-6-chloro[1,2,4]triazolo[1,5-a]- pyridine-2-sulfonamide, were prepared by condensation of a 2-chlorosulfonyl[1,2,4]triazolo[1,5-a]pyridine compound with an aryl amine. The compounds prepared were found to possess excellent herbicidal activity on a broad spectrum of vegetation at low application rates.
Substituted N-aryl\x9b1,2,4!triazolo\x9b1,5-a!pyridine-2-sulfonamide compounds, such as N-(2,6-difluorophenyl)-5-methoxy-7-methyl\x9b1,2,4!triazolo\x9b1,5-a!pyridine-2- sulfonamide, N-(4-bromo-1-methyl-3-pyrazolyl)-8-chloro-5-methoxy\x9b1,2,4!triazolo\x9b1,5-a!p yridine-2-sulfonamide, and N-(2-fluoro-4-methyl-3-pyridinyl)-8-ethoxy-6-chloro\x9b1,2,4!triazolo\x9b1,5-a!p yridine-2-sulfonamide, were prepared by condensation of a 2-chlorosulfonyl\x9b1,2,4!triazolo\x9b1,5-a!pyridine compound with an aryl amine. The compounds prepared were found to possess excellent herbicidal activity on a broad spectrum of vegetation at low application rates.
The invention relates to 2-benzylthio-8-amino[1,2,4]triazolo[1,5-a]pyridines and a process for the preparation thereof. These compounds can be used for the preparation of 2-benzylthio[1,2,4]triazolo[1,5-a]pyridine compounds, which are important intermediates in the preparation of N-aryl[1,2,4]triazolo[1,5-a]pyridines.
The reaction is generally carried out by combining one molar equivalent of a 2-benzylthio-8-chloro[1,2,4]triazolo[1,5-a]pyridine compound with at least 3 molar equivalents of stannous chloride, one molar equivalent of stannic chloride, and an excess of hydrogen chloride or at least one molar equivalent of the alcohol.