Stereoselective photodimerisation of chalcones in the molten state

Abstract

Photodimerisations of chalcone and its derivatives in the molten state proceed efficiently and stereoselectively to give rac-anti-head-to-head dimers in all cases tested.

Photodimerization of heteroaryl chalcones: comparative antimicrobial activities of chalcones and their photoproducts

“…The close similarity of the 1 H and 13 C NMR patterns of the cyclobutyl moieties of product 9 with d-truxinic structure strongly suggests that the formation of cyclobutane ring occurs by anti head-to-head junction in product 9 (D' Auria et al, 2001;Toda et al, 1998;Turowska-Tryk et al, 2003).…”

“…Intramolecular photocycloaddition of chalcones, heteroaryl chalcones and their derivatives to give cyclobutane ring is the photochemical dimerization of a,b-unsaturated carbonyl compounds and particular of 1,3-diaryl-2-propen-1-one (chalcones) (D'Auria et al, 2000;Toda et al, 1998;Cesarin-Sobrinho and Netto-Ferreira, 2002;Turowska-Tryk et al, 2003;Ishikawa et al, 1994). It has been proven to be a fast and simple method to minimize a cyclophane ring to a tricyclic system.…”

“…It has been proven to be a fast and simple method to minimize a cyclophane ring to a tricyclic system. These reactions can be carried out in solid state (Cesarin-Sobrinho and NettoFerreira, 2002), molten state (Toda et al, 1998) and solution by UV-Visible irradiation (D'Auria et al, 2001), with variable results in terms of product composition and yield. Although, photodimerization of chalcones have been studied especially in solid state (Turowska-Tryk et al, 2003), few studies found for the photodimerizations of chalcones in solution.…”

Photochemical Generation of Cyclophanes from 1,3,5‐Trisubstituted Benzenes with Chalcone Chromophores

“…However, structures of the dimers, obtained in solution, in the crystalline state and in the melt, [24] led to a very long and controversial discussion, until X-ray studies revealed, that in solution and in the molten state anti-head-to-head cycloadditions take place, whereas in the crystalline state syn-head-to-tail processes occur. [24,25] In principle, the photochemical behavior of the benzene derivatives studied here, with chalcone chromophores in 1,3,5-positions, resembles the behavior of the parent system -in solution as well as in the crystalline state. A special aspect is given by the threefold consecutive [2π+2π] cycloaddition of 7 which leads in anti-head-to-head processes to [4.4.4] (1,3,5)cyclophanes 8.…”

Photochemistry of Cyclobutanes: Synthesis and Reactivity

“…Heating the crystalline material to 60 • C and irradiating the melt with light from a 400-watt mercury vapour lamp for 24 h results in exclusive formation of the racemic anti-head-to-head dimers 197 141 . Asokan and his coworkers 142 …”