Thiopyran

Thiopyran

Organic Synthesis

Published in Suresh C. Ameta, Rakshit Ameta, Garima Ameta, Sonochemistry, 2018

Chetna Ameta, Arpit Kumar Pathak, P. B. Punjabi

Pourabdi et al. (2016) synthesized various derivatives of thiopyrano[4,3- b]pyran structure via a multicomponent procedure starting from tetra- hydro-4H-thiopyran-4-one, aromatic aldehydes and malononitrile. This reaction takes place using catalytic quantities of LiOH-H2O in one pot under ultrasonic conditions and in an ethanolic medium.

Theoretical investigation of vinylogous anomeric effect on 4-halo-4-H-pyran and 4-halo-4-H-thiopyran molecules

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Journal Information

Published in Journal of Sulfur Chemistry, 2018

Neda Najjari Milani, Reza Ghiasi, Ali Forghaniha

Figure 1 presents the structures of 4-halo-4-H-pyran and 4-halo-4-H-thiopyran molecules in planar and puckered conformations. Table 1 shows the absolute energy and relative energy values of these molecules. These values show that puckered form is more stable than planar form in all studied molecules. It can be found, the energy difference between two isomers decrease in the presence E = O and S in compared to E = CH2. The most relative energy values are observed in the presence of X = F. In addition, relative energy values decrease with the decrease in electronegativity of X. More stability of the puckered conformation is attributed to vinylogous hyperconjugative AE (Figure 2). Figure 2 presents the canonical (resonance) structure depicting the proposed hyperconjugative interaction. The following sections illustrate this effect.

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Organic Synthesis

Theoretical investigation of vinylogous anomeric effect on 4-halo-4-H-pyran and 4-halo-4-H-thiopyran molecules