The Photochemistry of 5,6-Dimethylidene-2-norborananone. Synthesis andDiels-Alder Reactivity of 2,3-Dimethylidenebicyclo-[2.1.1]hexane
作者:Luis Schwager、Pierre Vogel
DOI:10.1002/hlca.19800630508
日期:1980.7.9
2,3-Dimethylidenebicyclo [2.1.1]hexane (4) was isolated from direct irradiation (253.7 nm) of 5,6-dimethylidene-2-norbornanone (3). Quenching experiments at 253.7 nm, as well as direct and sensitized irradiations at >300 nm suggested that a high vibrationally excited S1- or a S2-state is required for the photodecarbonylation of 3 in contrast with other β, γ-unsaturated ketones for which α-cleavage
从5,6-二甲叉基-2-降冰片烷酮(3)的直接照射(253.7 nm)中分离出2,3-二亚甲基双环[2.1.1]己烷(4 )。在253.7 nm处进行淬火实验,以及在大于300 nm处进行直接和敏化辐照,表明3的光脱羰基化需要高振动激发的S 1-或S 2-态,而其他β,γ-不饱和酮α裂解以较低的激发能发生。新的二烯4在甲苯中与四氰基乙烯(k(1mol -1 s -1))=(3.1±0.34)·10 -3)和(6.2±0.11)·10反应-3苯只有60倍,比更慢2,3- dimethylidenenorbornane (5)和大约 速度是2,3-二甲基亚砜-syn 1,4,5,6-四甲基双环[2.1.1]-己烷(9)的850倍。