NOVEL HETEROCYCLOADDITION REACTION OF GLYCALS

Diacyl thione species 1 has been generated and reacted in situ with bo th pyranoid and furanoid glycals to form novel [4 + 2] cycloadducts. F actors such as protecting groups and configuration of substituents in the glycals along with medium effects were varied to discover influenc es on face selectivity and reactivity. A qualitative correlation of re activity with the HOMO-LUMO gap between the glycal (HOMO) and the hete rodienic species (LUMO) is observed. In one example, the isolation of byproducts suggests that the cycloaddition may in fact be stepwise.