1,2- and 1,4-Additions to methyl 2- and 3-phenylazo-glycopyrano-2-enosides

Abstract

Syntheses of methyl 4,6-O-benzylidene-2,3-dideoxy-3-phenylazo-α-D-erythro-hexopyrano-2-enoxide (1) and the corresponding 2-phenylazo-compound (2) are described: they differ in their behaviour (i) towards nucleophiles—whereas for compound (1) there is 1,4-addition across the structural component –NN–[graphic omitted]–, for compound (2) a rearrangement of the unsaturated system ensues, and (ii) towards dimethylsulphoxonium methylide which adds a methylene group at the olefinic bond in compound (2), but with which 1,4-addition occurs with compound (1).