Recrystallization of 1 and 2 from ethylene glycol afforded, respectively, a dimerization reaction product, 3, and the initial solid phase. Single-crystal XRD data for 2 could only be obtained using synchrotron radiation, while we failed to obtain a crystal structure of 1 using single-crystal or powder X-ray diffraction. Two novel pyridine-2-yl-containing ketones, 1 and 2 (Scheme and Fig. 1 ▸), were synthesized as described below, and recrystallized from ethanol. We aimed to synthesize pyridine-substituted representatives of this family in order to fix olefin fragments in photoreactive positions using hydrogen bonding or coordination bonding as described by Nagarathinam et al. However, our numerous attepts to carry out photocycloaddition in these compounds were unsuccessful. Many of the compounds previously reported by us, including 1,5-diarylpentenynones (Golovanov et al., 2013 ▸ Vologzhanina et al., 2014 ▸ Voronova et al., 2016 ▸1) and cyclic ketones with vinylacetylene fragments (Voronova et al., 2018 ▸) in crystals exhibit coplanar packing with a distance between the olefin fragments of less than 4.2 Å thus, they satisfy the Schmidt (1971 ▸) criteria for a solid-state cycloaddition to occur. Both trans– cis isomerization and cycloaddition reactions can be observed depending on the nature of the substituents on the alkyl chain (Vatsadze et al., 2006 ▸). Vinyl-substituted ketones are known to take part in photo-initiated reactions both in the solid state and in solution (Hopkin et al., 1991 ▸ Vatsadze et al., 2006 ▸).
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