Topochemical dimerization of non-parallel double bonds: 7-methoxycoumarin

6,7,8-Trimethoxycoumarin fromCryptocarya bracteolata

“…1). The compound complements the list of coumarins having methoxy (and/or hydroxy) groups in the 5 to 8 positions of the coumarin fused-ring, i.e., 6-methoxy- (Bauers et al, 2002;Gnanaguru et al, 1985), 7-methoxy- (Bhadbhade et al, 1984;Gnanaguru et al, 1984;Gnanaguru et al, 1985;Ramasubbu, et al, 1981;Ramasubbu et al, 1982), 8-methoxy- (Baures et al, 2002;Gnanaguru et al, 1985), 5,7-dimethoxy- (Ye & Fan, 2007), 7-hydroxy-6-methoxy- (Kimura et al, 1980), 7-hydroxy-5,6-dimethoxy- (Wagner et al, 1974) and 7-hydroxy-6,8-dimethoxy- (Li et al, 2001) coumarins.…”

“…For the crystal structures of coumarins having methoxy (and/or hydroxy) groups in the 5 to 8 positions, see: Baures et al (2002); Bhadbhade et al (1984); Gnanaguru et al (1984Gnanaguru et al ( , 1985; Kimura et al (1980); Li et al (2001); Ramasubbu et al (1981Ramasubbu et al ( , 1982; Wagner et al (1974); Ye & Fan (2007).…”

Molecular structures and crystal packings of 2-styrylquinoxaline derivatives

“…Note that, in the excited state, the strength of the π orbital interaction in the dimer is more important for the implementation of PCA than geometric parameters [27][28][29][30][31]. In all cases of implementation of the PCA reaction in the crystals with distances between the ethylene groups exceeding the Schmidt criterion, a strong π orbital interaction in the dimer was noted in the excited state.…”

Solvent‐Free Photosynthesis of Cyclobutanes: Photodimerization of Crystalline Olefins

“…In spite of the large distance of separation, they dimerize in the solid state. In compounds 6-12 listed in Scheme 5 and Table 5, the separation distances between reactive double bonds are less than 4.2Å, yet they do not undergo dimerization upon photolysis 49,50,52,73,87 . The exceptional situations in all these cases can be understood qualitatively by invoking the 'reaction cavity' concept.…”