A flexible route to new spirodioxanes, oxathianes, and morpholines

This work describes a modular efficient route to 10-aza-4-thia-, 10-aza-4-oxa-, and 10-oxa-4-thia-1,7-dioxaspiro[5.5]undecanes. The synthetic pathway relies upon the iterative nucleophilic substitution of 1,3-dichloropropan-2-one O-benzyloxime by solketal derivatives. The oxime key-intermediates, submitted to an acidic deprotection-spiroacetalization process, afforded these original spiroketal compounds in three steps, few purifications, and very good yields.