Photochemistry of 2,6-cyclooctadienone and 2,4-cyclooctadienone

Abstract

Irradiation of 2,6-cyclooctadienone (1) in inert solvents affords in modest yield tricyclo[3.2.1 .02a6]octan-8-one, whose structure was proven by chemical degradation. Irradiation of 1 in reactive solvents such as methanol or furan gives addition products derived from a ground-state intermediate, 2-fruns,6-cis-cyclooctadienone.Photolysis of 2,4-cyclooctadienone, 2, in inert solvents gives low yields of the trans, head-to-head, 2 + 2 dimer, 16, resulting from dimerization at the a,@ positions of each dienone molecule. In methanol and furan adducts resulting from trapping of a mono-trans-dienone are formed. Possible pathways for the formation of the various products are discussed. s part of the tremendous amount of investigation A into the photochemistry of carbonyl compounds, cyclic enones of various ring sizes have received considerable attention.* Recent studies of the photochemical behavior of medium-ring unsaturated ketones have uncovered a multitude of interesting transforma-(1) Supported in part by a grant from the Robert A. Welch Foun-( 2 ) See, for example, R. 0. Kan, "Organic Photochemistry," Mc-dation. Graw-Hill Book Co., Inc., New York, N. Y., 1966, Chapters 3 and 4.tions. The eight-membered ring conjugated enones 2-cycloocten-1-one3 and 2,4,6-cyclooctatrien-l -one4 have been found to undergo isomerization to strained trans enones, which in turn undergo thermal cycloadditions and dimerizations, and in the latter case,(3) (a) P. E. Eaton and I<. Lin,

Vanadium-catalyzed epoxidation of cyclic allylic alcohols. Stereoselectivity and stereocontrol mechanism

“…Hydrolysis of the benzoate with NaOH/methanol gave 1.6 g (49%) of 10 in 99% purity. 10: bp 57 °C (1.2 mm) (ref 44, 49-52 °C (0.3 mm)).…”

Die symmetrischen Cyclooctadienine: 1,5‐Cyclooctadien‐3‐in und 1,3‐Cyclooctadien‐6‐in

“…Die olefinischen Protonen erzeugen scharfe Signale bei 6 = 6.40 (d, ?I = 8. 5 Hz, 3-H), 5.94 (m, 4-H), 6.10 (4 Linien, 5-H), 5.95 ( Chem. Ber.…”

Homolytic rearrangements of bicyclo[2.2.0]hexane and bicyclo[3.2.0]heptane

“…110 "C; yield 23%; 8, 1.2-1.6 (6 H, m), 1.6-1.9 (2 H, m), 1.9-2.4 (2 H, m), and 2.5-2.9 (2 H, m). (18).-2-Hydroxybicyclo[3.2.0]heptane was made by reduction (LiAlH,) of bicyclo[3.2.0]heptan-2-one 35 and shown to consist of ? mixture of the cis-(95%) and trans-(5%) isomers.…”