1,3-Butadiene photodimerization

Chloranil, photocycloaddition with butadiene, 474 Chlorophylls, 552 Chu, N. Y. C 439 Ciamician, G., 1, 2,459 Cinnamic acid, solid state photodimerization, 476... 

Dienes (17) and (18) may not actually be photoproducts but may arise from thermal rearrangement of m-l,2-dialkenylcyclobutanes.<8,9) As in the photodimerization of butadiene, the product distributions of sensitized... 

The first photochemical reactions to be correlated with PMO theory were the dimerizations of anthracene, tetracene, pentacene, and acenaphthylene. 36> More detailed energy surfaces for the photodimerization reactions of butadiene have also been calculated. 30> In the category of simplified calculations lie studies of the regiospecificity of Diels-Alder reactions 37>, and reactivity in oxetane-forming reactions. 38,39) jn these... 

Scheme 3 Asymmetric [2-1-2] photodimerization of 1,3-butadiene derivatives in the mixed crystals [42]...

The L-B films offer some advantages over aqueous-hydrocarbon interfaces of micelles and the related assemblies discussed above in terms of the magnitude of their orienting ability and the ease of interpretation of selectivity in photoreactions conducted in them. Molecules in the films have very little freedom of motion (stiff reaction cavities), their interfaces are very well defined, and therefore the alignment of reactant molecules can be readily expressed in the products. Photodimerization of stilbazole derivatives 62, N-octadecyl-l-(4-pyridyl)-4-(phenyl)-l,3-butadiene, (63), surfactant styrene derivatives 64 and 65, and cinnamic acids have been carried out in L-B films [18, 196-200], In all cases, single isomeric head-head dimers are obtained. Geometric isomerization of olefins has not been observed in competition with photodimerization. Independent of the location of the chromophore (i.e.,... 

Recent reports detail a computational analysis of the photodimerization of 1,3-butadiene that located conical intersections for concerted [4+4] and [2+2] cycloaddition paths [19,20] and have correlated these results with the products observed experimentally [21]. 

A second method for the photodimerization of butadiene is the direct irradiation of solutions of butadiene with 2537 A. radiation. Less than 10% of the butadiene is converted to dimers in this way. The dimers that are obtained are (in the order of decreasing yield) 2-vinylbicyclo-... 

These equations were used subsequently to account for the thermal and photochemical dimerization of butadiene, the Diels-Alder addition between two acrolein molecules, where the asynchronous nature of the cycloaddition was demonstrated, and the endo mechanism. These equations provided a demonstration of the symmetry rules for the cycloaddition reactions, and could account for the photodimerization of trop-one. 

Photodimerization of isoprene to 1,5-dimethylcyclo-octa-l,5-diene and 1,6-dimethylcyclo-octa-1,5-diene is discussed. Evidence has been presented for a multistep process in the oligomerization of butadienes with nickel... 

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