A simple synthesis of bis-annulated bicyclo[2.2.2]octenones containing a β,γ-enone chromophore and photochemical reactions: a new entry into angular tetraquinane and other polycyclic systems

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

“…The high triplet energy of acetone (E T = 332 kJ mol –1 ) 126 and its favorable properties as a solvent make it the most commonly used triplet sensitizer. Recent examples for this procedure can be found in the synthesis of basketenes en route to diademenes by de Meijere, Schreiner, and co-workers 127 or in the intramolecular [2 + 2] photocycloaddition of two cyclopentenes performed by Singh et al 128 Xanthone (E T = 310 kJ mol –1 ) 129 was applied by Gleiter, Yang, and colleagues as sensitizer to prepare the cage acetal 53 by intramolecular [2 + 2] photocycloaddition of substrate 52 ( Scheme 16 ). 130 Sensitized intermolecular photocycloaddition chemistry was successfully performed by Klimova et al to obtain the cis-anti-cis photodimers of 3-ferrocenyl-substituted cyclopropenes.…”