Reactions of alpha,alpha'-dihydroxy ketones with phosgene. Structural requirements for spiro epoxy carbonate formation

[reaction: see text] Apha,alpha'-dihydroxy ketones having two OH groups that can come into close proximity react with phosgene in the presence of DMAP to produce 1,3-dioxane-2,5-diones. When covalent bonding in this manner is prohibited, alternate reaction pathways can in principle be adopted. Of these, the generation of spiro epoxy carbonates is shown to be feasible in three examples. In other cases, the alpha-ketol rearrangement precedes diacylation.