Mechanistic and Exploratory Photochemistry. XV.¹ The Relation of Cyclohexenone to Cyclohexadienone Rearrangements

Cyclopropenylcarbinol Derivatives as New Versatile Intermediates in Organic Synthesis: Application to the Formation of Enantiomerically Pure Alkylidenecyclopropane Derivatives

“…The only products formed were the two a,b-unsaturated ketols 4 and 5, formed in almost equal amounts (each in 22-25 % isolated yields), as a result of the isomerization of the postulated intermediate 3 through a cleavage of the two peripheral s bonds (Scheme 2). [14] Oxabicyclobutanes have been also postulated several times as intermediates in various thermal and photochemical reactions, [15] but could also never be detected. However, recent high-level quantum chemical studies on the unimolecular (and acid-catalyzed) fragmentation of such intermediates suggested that this compound should be stable enough to be detected in chemical reactions.…”

Photochemische Reaktionen. 95. Mitteilung. Zur Photochemie konjugierter Epoxy‐enone: Die UV.‐Bestrahlung von 9‐Isopropyl‐6‐methyl‐9, 10‐epoxybicyclo [4.4.0] dec‐1‐en‐3‐on

“…Es wird lediglich C ( y ) , 0-Spaltung (1 +a) beobachtet, wobei sich das Spaltprodukt a in einem Hauptprozess unter Ringverengung (1,2-Alkylverschiebung) zum ungesattigten 1,5-Diketon S6) stabilisiert und in einer Nebenreaktion unter 1,2-Wanderung des Isopropylsubstituenten in das zu 8 isomere 1,5-Diketoii b umwandelt. Die nicht isolierte Verbindung b') reagiert vermutlich rasch unter n, n*-Anregung im Sinne einer ctTyp AwPhotoisomerisierung [5] zur Cyclopropanverbindung 9 (s. Schema 7). Schliesslich sei im Hinblick auf die Ergebnisse der I'hotolyse von 1 bei langwelligem Licht (s. unten) erwahnt, dass unter n, n*-Anregung 1 keine Desoxygenierung zu 7 erfahrt (GC.-und 'H-NMR.-Analyse).…”

Photochemical studies of some 2-cyclohexenones

“…The spectroscopic investigation of six steroidal ketones (5)(6)(7)(8)(9)(10) by phosphorescence excitation and emission methods was carried out by Keams and coworkers in 1968 (3, 4). Direct absorption and phosphorescence excitation 3 * techniques allowed location of the (n,TT ) states.…”