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