Synthetic Utility of Alkenylcyclobutenedione Monoketals. Michael Additions and the Synthesis of a Natural Benzofuranosesquiterpenequinone

Article abstract of DOI:10.1021/jo00091a013

A new synthetic route to highly substituted cyclobutenones is reported.This involves the 1,6-addition of both heteroatom- and carbon-based nucleophiles to 4,4-dimethoxy-3-ethenyl-2-methylcyclobuten-1-one (8) to give further functionalized cyclobutenedione monoketals.These ketals function as precursors to quinones as illustrated by the synthesis of the natural benzofuranosesquiterpene 23.