Synthetic studies towards 4,10-diaza-1,7-dioxaspiro[5.5]undecanes: access to 3-aza-6,8-dioxabicyclo[3.2.1]octan-2-one and 2H-1,4-oxazin-3(4H)-one frameworks

Synthetic approaches towards 4,10-diaza-1,7-dioxaspiro[5.5]undecanes starting from 1,3-dichloroacetone and solketal derivatives are explored. The method relies on the preparation of a key bis-substituted dihydroxy-protected oxime, which would undergo a final acidic deprotection–spiroacetalization process. Although the desired diazaspiroketal framework could not be obtained, our conditions led to the unexpected 3-aza-6,8-dioxabicyclo[3.2.1]octan-2-one 18 or to the oxazinone 32 in good yields.