A homochiral microporous hydrogen-bonded organic framework (HOF-2) based on a BINOL derivative has been synthesized and structurally characterized to be a uninodal 6-connected {3(3)5(5)6(6)7} network. This new HOF exhibits not only a permanent porosity with the BET of 237.6 m(2) g(-1) but also, more importantly, a highly enantioselective separation of chiral secondary alcohols with ee value up to 92% for 1-phenylethanol.
Zn(OTf)(2) acts as an excellent catalyst precursor for addition of various amine N-H bonds to carbodiimides under an atmosphere of air, offering a convenient synthesis of substituted guanidines with high functional-group tolerance. A Zn-N amido species is shown to act as the active species.
The organocatalytic enantioselective tandem aldol-cyclization reactions of α-isothiocyanato imides and activated carbonyl compounds, such as isatins, an α-ketolactone and a 1,2-dione, have been studied with cinchona alkaloid-derived thiourea-catalysts. This methodology provided an easy way to access enantiomerically enriched spirobicyclic thiocarbamates with high yields and good to excellent stereoselectivity, which have been demonstrated to be useful precursors for the synthesis of biologically active molecules.
An organocatalyzed direct Mannich reaction of unactivated α-styrylacetates was realized for the first time. By using a quinidine-derived C6'-urea catalyst, the direct Mannich reaction of α-styrylacetates and N-tosylimines gave the desired β-amino esters in high yields, diastereoselectivities, and ee values. The reaction provides a highly stereoselective (up to 96:4 dr and 97% ee) and the most straightforward synthesis of functionalized N-tosylated β-amino esters. The products can be used as precursors for the highly selective synthesis of tetrahydrofuran derivatives.
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