Conclusion

In conclusion, the author has developed new methods for the synthesis of medium-sized cycloalkenes by utilizing 4π-electrocyclic reaction of fused cyclobutenes. The fundamental strategy using readily available high-strain energy raw materials to obtain products with high-strain energy that are difficult to access was well worked in the developed methods. The author first studied fused cyclobutenes’ properties where the substituent effects and the influence of temperature of 4π-electrocyclic reaction giving short-lived cis,trans-cycloalkadiene intermediate were disclosed. Two methods for converting the intermediate to medium-sized ring were developed based on the properties identified, where selective reactions for the respective double bond were employed. The cis-selective reaction led to a novel method for medium-sized trans-cycloalkenes synthesis bearing several functional groups, where the short-lived cis,trans-siloxycycloalkadiene intermediates were selectively modified through enol silyl ether activation by fluoride anion and successive reaction with various electrophiles.