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Upstream product

• 908094-04-2 phenyldiazomethane 
• 118-75-2 chloranil 
• 645-49-8 cis-stilben 
• 103-30-0 (E)-1,2-diphenyl-ethene 

Downstream Products

• 645-49-8 cis-stilben 
• 103-30-0 (E)-1,2-diphenyl-ethene 
• 118-75-2 chloranil 

Relevant academic research and scientific papers

Oxetanes from [2+2] cycloaddition of stilbenes to quinone via photoinduced electron transfer

The photochemical coupling of various stilbenes (S) and chloranil (Q) is effected by the specific charge-transfer (CT) activation of the precursor electron donor-acceptor (EDA) complex [S, Q], and the [2+2] cycloaddition is established by X-ray structure elucidation of the crystalline transoxetanes formed selectively in high yields. Time-resolved (fs/ps) spectroscopy reveals the (singlet) ion-radical pair 1[S·+, Q·-] to be the primary reaction intermediate and thus unambiguously establishes for the first time the electron-transfer pathway for this typical Paterno-Buchi transformation. The alternative cycloaddition via the specific activation of the carbonyl component (as a commonly applied procedure in Paterno-Buchi couplings) leads to the same oxetane regioisomers in identical molar ratios. As such, we conclude that a common electron-transfer mechanism applies via the quenching of the photoactivated quinone acceptor by the stilbene donor to afford triplet ion-radical pairs 3[S·+, Q·-] which appear on the ns/μs time scale. The spin multiplicities of the critical ion-pair intermediate [S·+, Q·-] in the two photoactivation methodologies determine the time scale of the reaction sequences (which are otherwise the same), and thus the efficiency of the relatively slow ion-pair collapses (k(C) ? 108 s-1) to the 1,4-biradical that ultimately leads to the oxetane product.

Photodynamics of the Paterno-Buechi cycloaddition of stilbene to quinone. Unusual modulation of electron-transfer kinetics by solvent and added salt

Oxetanes are produced in the Paterno-Buechi cycloaddition of stilbene (S) to quinone (Q) via an efficient photoinduced electron transfer. Kinetics analysis of the time-resolved absorption spectra over three distinctive (ps, ns, μs) timescales establishes the coupling (kC) of the initially formed ion-radical pair 3[S+?, Q-?] to the 1,4-biradical ?SQ? as the critical step toward oxetane formation. The (rather slow) rate constant of kC ≤ 107 s-1 in acetonitrile must compete with other faster decay pathways of the ion pair involving ionic separation, ion exchange (with added salt) and back electron transfer. As such, solvent polarity and donicity as well as added salts play an unusually prominent role in modulating the ion-pair microdynamics. Donor-acceptor complexation of the photoexcited quinone with the solvent and cis→trans isomerization of (Z)-stilbene must also be considered in the overall photodynamics of electron transfer.

Photoinduced Reactions of Chloranil with Stilbene Derivatives and α,β-Unsaturated Carbonyl Compounds

Photolysis of chloranil (CA) with Z- or E-stilbenes 1-5 3CA* and the alkenes is involved in the cycloaddition and isomerization.Photolysis of CA with ethyl (E)- or (Z)-cinnamate (E-22 or Z-22), ethyl 3-nitrocinnamate (E-23 or Z-23), benzalacetone (E-24 or Z-24), chalcone (E-25 or Z-25) and (E)-4-fluorochalcone (E-26) in benzene or in acetonitrile gave trans-oxetane products 27-31 respectively in good yield (72-95percent) and resulted in slight E-to-Z and considerable Z-to-E isomerizations without SET-process involvement.

SOLVENT EFFECTS IN THE CONVERSION OF PHENYLDIAZOMETHANE INTO STILBENE AND SPIROOXETANE IN THE REACTION WITH CHLORANIL

A stereochemical study was made of the reaction of phenyldiazomethane(1) with chloranil(2) at 20 deg.C in 28 aprotic solvents.The products were trans-spirooxetane(4) and cis-trans mixtures of stilbene(3) (ca. 2-5 times cis-rich).The molar ratios of cis-3 to the sum of the trans-3 and 4 tended to increase, whereas the 4 to trans-3 ratios decrease with the increase in the solvent basicity and polarity.These effects of solvents on the product distributions were interpreted in terms of the effects of the solvent basicity and polarity on the stereoselective formation of the diazonium betaine intermediate and on the conformational isomerism.Moderately successful linear-free-energy(LFE) relationships were established for these product ratios with the aid of the combination of the empirical solvent basicity parameter, D?, and the Kirkwood function, f(ε), or ET values as the solvent polarity parameters.

Reactions of Aryldiazomethanes with Chloranil

The reactions of several aryldiazomethanes (1a: p-tolyl; 2b: phenyl; 1c: p-chlorophenyl) with chloranil gave stilbenes (3) and spiro-oxetanes (4) at 20 deg C in tetrahydrofuran or 1,2-dichloroethane.The isomer ratios of 3 were ca. 2 to 3:1 in favor of cis, depending on the solvents and on the substituents 1.In the case of 4, however, stable trans-isomers were selectively formed.On the other hand, the presence of added CH3OH supressed the formation of 3 and 4 and, instead induced redox reactions giving α,α-dimethoxyarylmethanes and tetrachlorohydroquinone (6).In these redox reactions, the acid decompositions of 1 with 6 were also found.However, the presence of CF3CH2OH allowed the formation of considerable amount of 3 and 4, along with the redox products.The mechanism of these reactions will be discussed.