Lewis Acid Catalyzed Ring-opening Reaction Of Cyclobutanone Compounds

Cyclobutanone compounds have been widely studied due to their unique reactivity,and being applied to various transformations as vital intermediates.Significant progess has been made on the ring-expansion reaction of cyclobutanones through oxidative addition and β-carbon elimination,but inevitably using the transition metals such as rhodium,nickel and palladium.In addition,Lewis acid promoted ring-opening reactions of 3-donorsubstituted cyclobutanones have been reported,and stoichiometric catalysts were mostly employed.Therefore,it is important to develop a simple and efficient ring-opening reaction of cyclobutanones.And we decided to employ simple cyclobutanones to construct unsaturated chain and cyclic compounds catalyzed by catalytic amounts of Lewis acid.The research contents include the following two aspects:The Lewis acid catalyzed ring-opening reaction of β,β-diphenyl cyclobutanone was developed,which provided additional efficient access to conjugated enones with good functional group tolerance under mild conditions.It was found that water plays an important role in the reaction and can significantly increase the yield.Besides,the orthosubstituted substrates afforded the Z-configuration in excellent selectivity.Finally,the reaction mechanism was explored by control experiments and in-situ tracking experiments.The product derivatization and gram-scale experiments further showcased the synthetic utility of the reaction.The intramolecular ring-opening\Friedel-Crafts reaction of benzylcyclobutanones was further investigated.With Lewis acid as the catalyst,β-benzylcyclobutanones were subjected to the ring-opening aromatization reaction to obtain polysubstituted naphthalene,which was also applicable to the synthesis of fused-ring compounds.In addition,the reaction was carried out under mild conditions with a low-cost catalyst,and the system was compatible with a wide range of functional group.Finally,27 examples of naphthalene derivatives were synthesized in yields of 33-99%,with water as the only byproduct.