Mild and Highly Efficient Method for the Silylation of Alcohols Using Hexamethyldisilazane Catalyzed by Iodine under Nearly Neutral Reaction Conditions
A simple and highly efficient method for the preparation of tetrasubstituted NH-pyrrole from a wide range of chalcones and diethyl iminodiacetates via a Cu(OAc)2-promoted oxidation/[3+2]cycloaddition/aromatization cascade reaction has been developed. This reaction proceeds through dehydrogenations, deamination, and oxidative cyclization, affording the corresponding products in good to excellent yields. This convenient methodology for constructing tetrasubstituted NH-pyrroles has several advantages over existing methods, such as the use of easily accessible chalcones and readily available diethyl iminodiacetates, and mild reaction conditions. A wide range of substrates are tolerated.
A rapid, clean, and highly efficient method for synthesis of dihydropyrano[3,2-c]chromene derivatives by one-pot, three-component condensation of aromatic aldehydes, malononitrile, and 4-hydroxycoumarin using DABCO as catalyst in solvent-free neat conditions is described. The present method has the advantages of mild reaction conditions, short reaction times, easy isolation of products, and excellent yields.
A highly efficient method for the construction of oxindole-pyrrolidone-thiazolidinone bispirocyclic heterocycles bearing three contiguous chiral centers including two quaternary one via a Michael/cyclization cascade reaction has been developed. Using bifunctional cinchona-derived squaramide as catalyst, the reactions of 3-isothiocyanato oxindoles with unsaturated thiazolidinone derivatives proceeded smoothly under mild reaction conditions to afford a series of complex chiral oxindole-pyrrolidone-thiazolidinone bispirocyclic heterocycles in high yields (up to 99%) with excellent diastereo- and enantioselectivities (up to >99:1 dr, >99% ee).