One-Pot Synthesis of Glycosyl-β-azido Ester via Diazotransfer Reaction Toward Access of Glycosyl-β-triazolyl Ester

A concise and efficacious one-pot protocol for the synthesis of novel glycosyl-β-azido ester 3 from glycosyl olefinic ester 1 under mild conditions has been devised. The β-aminoester, formed by the conjugate addition of ammonia on olefinic ester, undergoes a metal-catalyzed diazotransfer reaction to furnish glycosyl-β-azido ester. The optimized conditions for diazotransfer reaction indicate that imidazole-1-sulphonyl azide and K2CO3 give the best results in the presence of ZnCl2. A diverse range of novel regioselective triazolyl glycoconjugates 6a–u have been achieved in high yields via 1,3-dipolar cycloaddition of compound 3 with various alkynes in the presence of CuI/DIPEA. Structures of all the compounds have been elucidated using IR, NMR, MS, and elemental analysis, and four of them (3a, 3b, 4b, and 6a) have also been characterized by single crystal X-ray diffraction analysis.