73675-30-6Relevant articles and documents
The Structure of 1,3-trans-Bis(4-chlorophenyl)-2,4-trans-di(4-pyridyl)cyclobutane, a Photodimer of 4'-Chloro-4-styrylpyridine
Busetti, V.,Valle, G.,Zanotti, G.,Galiazzo, G.
, p. 894 - 897 (1980)
The crystal structure of 1,3-trans-bis(4-chlorophenyl)-2,4-trans-di(4-pyridyl)cyclobutane, C26H20Cl2N2, has been determined from 1765 three-dimensional intensities, collected with an automated Philips PW 1100 four-circle single-crystal diffractometer and refined to R=0.058.Cell constans are a=16.307 (8), b=13.907 (2), c=9.666 (3) Angstroem, β=94.47 (5) deg, Z=4; the space group is P21/n.The cyclobutane ring has a puckered conformation, and the two dihedral angles are 19.1 and 19.2 deg.The structure determined shows that the dimerization process is a head-to-tail reaction.
[2+2] Photodimerization of Stilbazoles Promoted by Oxalic Acid in Suspension
Nguyen, Thanh Binh,Nguyen, Tuan Minh,Retailleau, Pascal
supporting information, p. 4682 - 4689 (2020/04/15)
In this study, a very simple technique to perform efficiently photodimerization of some vinylpyridines is reported. By irradiating a stirred mixture of several stilbazoles with solid oxalic acid dihydrate dispersed in a nonpolar (i.e., cyclohexane) or moderately polar (benzene, dichloromethane, dioxane) solvent, the corresponding dimeric cyclobutane adducts were obtained in high yields and excellent regio- and stereoselectivities. The strategy could also be applied successfully to oily, waxy, or even insoluble stilbazoles. Moreover, the oxalic acid loading could be lowered to substoichiometric amounts. When further optimizations were needed, our strategy was found to be highly flexible to identify other oligocarboxylic acids as alternative additives to improve, or even overturn, the regioselectivity. Oxalic acid and other oligocarboxylic acids were found to be capable of orienting more than 50 stilbazoles toward photodimerization under these conditions.
Thiourea as a template for photodimerization of azastilbenes
Bhogala, Balakrishna R.,Captain, Burjor,Parthasarathy, Anand,Ramamurthy
supporting information; experimental part, p. 13434 - 13442 (2010/12/18)
In this study we have explored the potential of thiourea (TU) as a template to preorient stilbazoles and bispyridylethylenes (azastilbenes) in the crystalline state. TU is able to preorient eleven azastilbenes toward dimerization in the crystalline state. While cocrystals of these eleven olefins photodimerized to a single dimer expected based on crystal packing, pure crystals of these olefins either were nonreactive or gave a mixture of dimers. The differential photobehavior of the pure crystals and cocrystals highlights the importance of TU in templating the olefins in a photoreactive orientation in the crystalline state. X-ray crystallographic and photochemical studies have identified a few azastilbenes that photodimerize in spite of not being arranged in an ideal orientation in the crystalline state. These as well as a few examples already reported in the literature suggest that it is important to recognize that molecules could experience large amplitude motions in the crystalline state, especially when energized by light. Short-term lattice instability caused by photoexcitation can be effective in driving a photochemical reaction. Thus one should view the crystalline arrangement of molecules upon light exposure as dynamic rather than static as determined from X-ray structure analysis.
