New synthetic reactions using 2-Pytidyl related reagents

Abstract

Di-2-pyridyl carbonate (2-DPC) was conveniently prepared by the reaction of phosgene with 2-hydroxypyridine. Di-2-pyridyl carbonate could be effectively utilized as a coupling agent for the preparation of various useful and reliable active esters such as 2-pyridyl, succinimidyl, phthalimidyl, benzotriazol-1-yl, p-nitrophenyl, and pentachlorophenyl esters. It is found that the combination of 2-DPC and 4-dimethylaminopyridine (DMAP) is exceedingly effective in the direct thiolesterification of carboxylic acids. We have obtained a high degree of selectivity on the selective esterification of two structurally different carboxylic acids with equimolar amount of an alcohol using 2-DPC as a coupling agent. $\beta$-Keto esters were obtained in high yields by the reaction of 2-pyridyl esters with magnesium salt of a malonic acid monomethyl ester. Reaction of 2-pyridyl esters with sodium dimethyl malonate affords -acyl dimethyl malonates in high yields. Also 2-pyridyl esters were easily converted to N-acryl imidazoles or alcohols under mild conditions. Isothiocyanates are obtained in high yields when triethylammonium dithiocarbamates are treated with di-2pyridyl carbonate at room temperature. Di-2-pyridyl carbonate can be used as a dehydrating reagent for the preparation of niriles from aldoximes. Di-2-pyridyl carbonate is also effectively utilized as a carbonyl transfer reagent for the preparation of cyclic carbonates and 2-oxazolidones. Several synthetically useful active carbonates can be prepared from di-2-pyridyl carbonate and alcohols in the presence of 4-dimethylaminopyridine. Reaction of amines with di-2-pyridyl carbonate affords 2-pyridyl carbamates in high yields. Reaction of 2-pyridyl carbamates with 0.1 equiv of 4-dimethylaminopyridine in aqueous tetrahydrofuran affords the symmetrical ureas, whereas reaction of 2-pyridyl carbamates with amines affords the unsymmetrical ureas. Reaction of epoxides with S-2-pyridyl thiolacetate in the presence of cupric bromid...