73675-30-6

Upstream product

• 2502-99-0 (E)-4-(4-chlorostyryl)pyridine 
• 142937-28-8 4-(4-chloro-trans-styryl)-pyridine; hydrochloride 
• 108-89-4 picoline 
• 104-88-1 4-chlorobenzaldehyde 

Relevant academic research and scientific papers

The Structure of 1,3-trans-Bis(4-chlorophenyl)-2,4-trans-di(4-pyridyl)cyclobutane, a Photodimer of 4'-Chloro-4-styrylpyridine

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.

Combining topochemical [2+2] photoreactions and hydrothermal isomerisation for the regioselective and quantitative preparation ofrtct-pyridylcyclobutanes

A non-photochemical route for the regioselective and quantitative preparation of rtct-pyridylcyclobutane isomers is achieved from the combination of solid state [2+2] photoreactions and controlled isomerisations promoted either by Lewis or Bronsted acids under hydrothermal conditions. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012.

[2+2] Photodimerization of Stilbazoles Promoted by Oxalic Acid in Suspension

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.

Role of hydrogen bonds in molecular packing of photoreactive crystals: Templating photodimerization of protonated stilbazoles in crystalline state with a combination of water molecules and chloride ions

A difference in photobehavior and molecular packing between hydrated and anhydrous crystals of protonated trans-stilbazoles has been identified. While stilbazoles are not photoreactive in the crystalline state, upon protonation with HCl in the solid state they dimerized to a single dimer (anti-head-tail) when exposed to UV light. In these photoreactive crystals the protonated stilbazole molecules are arranged in a ladder-like format with the rungs made up of water molecules and chloride ions. A combination of water and chloride ion holds the protonated trans-stilbazoles through either N-H...O or N-H...Cl- interactions. Anhydrous protonated stilbazole crystals prepared by heating the 'wet' crystals under reduced pressure were inert upon exposure to UV light. As per X-ray crystal structure analyses these light stable crystals did not contain water molecules in their lattice. The current investigation has established that water molecules are essential for photodimerization of crystalline protonated trans-stilbazoles. To compare the reactivity of protonated trans-stilbazoles with that of protonated cis-stilbazoles, photoreactivity and packing arrangement of cis-4-iodo stilbazole?HCl salt was examined. This molecule in the crystalline state only isomerized to the trans isomer and did not dimerize. Thus, while the trans isomer dimerized and did not isomerize, the cis isomer only isomerized and did not dimerize in the crystalline state. To probe the role of cation...π interaction in the packing of protonated trans-stilbazoles, energies of various types of packing in the gas phase were estimated by MP-2 calculations and cation...π interaction was found to be unimportant in the packing of protonated trans-stilbazole crystals investigated here.

Thiourea as a template for photodimerization of azastilbenes

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.