Arylazo-glycenosides. Part V. Cycloadditions with methyl 5-O-benzoyl-2,3-dideoxy-3-phenylazo-α- and -β-D-glycero-pent-2-enofuranoside

Abstract

Methods for the formation of fused bicyclic systems in which one of the rings is furanoid have been examined by studying the addition of acrylonitrile to methyl 5-O-benzoyl-2,3-dideoxy-3-phenylazo-α-or -β-D-glycero-pent-2-enofuranoside. 1,4-Cycloaddition occurs across these azoalkenes. Diazomethane and dimethyloxosulphonium methylide undergo 1,2-cis-addition across the carbon–carbon double bond of the α-D-azoalkene. The stereochemistry of the products has been studied by n.m.r. spectral methods. The adduct from the diazomethane reaction extrudes nitrogen when heated, and the product undergoes cyclisation to give a 4′,5′-dihydro-1′-phenyl-(methyl 5-O-benzoyl-2,3-dideoxy-α-D-pentofuranosido)[3,2-c]-Δ²′-pyrazole and methyl 5-O-benzoyl-2,3-dideoxy-2,3-C-methylene-3-phenylazo-α-D-lyxofuranoside. Comment is made on the mechanisms of some of the reactions studied.