Halogen addition to some 1-C-substituted pyranoid glycals

Addition of bromine and chlorine to O-peracylated 1-CN-, COOMe-and CONH2-substituted glycals was studied under ionic and radical conditions. The main or exclusive products were the corresponding 2,3-trans-diaxial (3bromo-3-deoxy-alpha-D-heptopyranosylbromide)onic acid derivatives. Bromination of the O-peracetylated D-lyxo-hept-2-enopyranosononitrile and all chlorinations proved selective towards the 2-axial-3-equatorial (3-halogeno3-deoxy-alpha-D-heptopyranosylhalide)onic acid derivatives. Silver triflate promoted glycosylation of methanol was successful with each 2,3-trans-diaxial (3-bromo-3-deoxy-alpha-D-heptopyranosylbromide)onic acid derivative, however, several attempted nucleophilic substitution and elimination reactions gave the parent glycal only.

Automated summary

The study focused on the addition of bromine and chlorine to O-peracylated glycals, resulting in mainly 2,3-trans-diaxial (3-bromo-3-deoxy-alpha-D-heptopyranosylbromide)onic acid derivatives. Despite successful glycosylation reactions, most attempted nucleophilic substitution and elimination reactions only yielded the parent glycal.