141305-41-1Relevant articles and documents
Modulating reactivity and diverting selectivity in palladium-catalyzed heteroaromatic direct arylation through the use of a chloride activating/blocking group
Liegault, Benoit,Petrov, Ivan,Gorelsky, Serge I.,Fagnou, Keith
supporting information; experimental part, p. 1047 - 1060 (2010/04/04)
(Chemical Equation Presented) Through the introduction of an aryl chloride substituent, the selectivity of palladium-catalyzed direct arylation may be diverted to provide alternative regioisomeric products in high yields. In cases where low reactivity is typically observed, the presence of the carbon-chlorine bond can serve to enhance reactivity and provide superior outcomes. From a strategic perspective, the C-Cl bond is easily introduced and can be employed in a variety of subsequent transformations to provide a wealth of highly functionalized heterocycles with minimal substrate preactivation. The impact of the C-Cl functional group on direct arylation reactivity has also been evaluated mechanistically, and the observed reactivity profiles correlate very well with that predicted by a concerted metalation-deprotonation pathway.
New Methods for the Introduction of Substituents into Thiazoles
Begtrup, Mikael,Hansen, Lars Bo L.
, p. 372 - 383 (2007/10/02)
New methods for the regioselective introduction of substituents into thiazoles have been developed using thiazole, 2-phenylthiazole and 4,5-dimethylthiazole as representative thiazoles.Improved halogenation methods, displacement of hydroxy groups in combination with dehalogenation at C-5 yield all eight possible 2-phenyl-4-halo-, 5-halo and 4,5-dihalo-thiazoles in which halogen is chlorine and bromine.Peracid oxidation of the thiazoles gives the corresponding thiazole 3-oxides.These are not activated towards halogenation but are deprotonated with sodium hydride.The anion formed react with electrophiles such as paraformaldehyde, 2,2-dimethylpropanal, 2,2-dimethylpropanoyl chloride, hexachloroethane, tetrabromomethane, and dimethyl disulfide leading to the introduction of carbon substituents, halogen, and methylthio groups.In these reactions, the reactivity of the thiazole ring positions decreases in the order 2 than 5 than 4.Monoselectivity is low when halogen and methylthio groups are introduced since these substituents enhance the acidity of adjacent ring protons. 2-Phenyl-4,5-dihalothiazole 3-oxides lose the 5-halogen when treated with sulfite ion.Trimethyloxonium tetrafluoroborate O-methylates thiazole 3-oxides.Thiazole N-oxides also react with acetyl chloride and phosphorus oxychloride to afford chlorothiazoles in a non-selective manner.Phosphorus trichloride deoxygenates thiazole 3-oxides.
