Photochemische Reaktionen 115. Mitteilung [1]. Zur Photochemie konjugierter γ,δ‐Epoxyenone: Der Einfluss eines Hydroxylsubstituenten in ϵ‐Stellung

Abstract

On 'n,n*-or 'n,n*-excitation (A 2 347 or 1 = 254 nm), the E-hydroxy-y,Gepoxyenone 8 undergoes fission of the C(y)-0 bond followed by the cleavage of the C(S)-C(s) bond. This hitherto unknown sequence of reactions is evidenced by the structure determination of the new type products 10-17 and 25, including a synthetic proof for 12 and the X-ray analysis of 11 (X-ray data: triclinic P1; u = 7,386(2), b = 8,904(4), c = 9,684(5)A; = 82,29(4)0, p = 74,46(3)O, y = 82,29(3)0;The selective 'n,n*-excitation also induces competitive C(y)-C(S) bond cleavage to yield the bicyclic acetal 18 and a ketonium-ylide intermediate a, which photochemically forms a carbene b giving the allene 19 and the cyclopropene 20.On 'n,n*-excitation of the acetate 9 the initial C(y)-0 bond fission is, in contrast to the behaviour of the corresponding alcohol 8, followed by a 1,2-methyl shift affording (E/Z)-28 or by a cyclization-autoxidation process yielding the lactone 29. z = 2).

Photochemical Reactions 127th CommunicationPhotochemistry of Epoxy‐enones: Intramolecular Trapping of a Carbonyl Ylide

“…105 (24), 100 (IS), 99 (10). 93 ( I I ) , 91 (19), 87(74).79 (14),77(18),73(11),55 (12),43(57), 41 (17). .…”

“…9, 35.2, 39.7 (3 t, C(3), C(6'), C(7')); 84.9 (d, C(5')); 98.5 (d, C(4)); 38.0 (s, C(4')); 107.3 (s, C(1')); 158.4 (s, C(3')); 207.5 (s, C (2)). -MS.: 224 (2, M t , C13H2003), 142(18), 111 (12), 109(17),83(13),71 (12),69(10),55(58),43(100), 41 (19).…”

“…1:l mixture of 11 and 14 which can be assigned to 11): 25.2,25.4,25.5,27.7 (4qa,4 CH3),27.3,34.5 (2 t, C(4), C(5)); 75.4 (d, C(3)); 88.8 (d, C(8)); 117. 8 (d, C(9)); 39.8 (s, C(2)); 89.5 (s, C(6)); 140 (lo), 135 (13), 133 (I]), 123 (12), 121 (16), 109 (Il), 107 (14), 95 (loo), 93 (12), 91 (lo), 67 (lo), 43 (58), 41 (14). 136.5 -137.0" (ether).…”

“…193 (11). 163 (14), 121 (17), 105 (IS), 100 (22), 99 (12).93(10).91 (20),87(71), 79(11),77 (14), 55 (13),43(50), 41 (16). -3-(3', 3'-Ethylendioxy-I'-butenyl)-2.2,4-trimethyl-3-cyclohexen-I -one (8).…”