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Tetrahydro-1,4-thiazine-3,5-dione

“…The residue was subjected to kugelrohr distillation to give the product as colourless crystals which were directly suitable for the X-ray structure determination. Both IR and NMR (CD3SOCD3) spectra were in agreement with previously reported values [2], but we have also recorded 1 H-and 13 C-NMR data in CDCl3 (see Experimental Section and Supplementary Material). In the X-ray structure there are two distinct molecules (Figure 1, Tables 1 and 2) both of which show an "envelope" structure with the sulfur atom above the plane containing the imide function and two CH2 groups.…”

“…The residue was subjected to kugelrohr distillation to give the product as colourless crystals which were directly suitable for the X-ray structure determination. Both IR and NMR (CD 3 SOCD 3 ) spectra were in agreement with previously reported values [2], but we have also recorded 1 H-and 13 C-NMR data in CDCl 3 (see Experimental Section and Supplementary Material).…”

“…The simple heterocyclic compound tetrahydro-1,4-thiazine-3,5-dione (or thiomorpholine-3,5-dione) 1, the cyclic imide of thiodiglycolic acid 2, was first prepared in 1948 [1], and IR and NMR spectroscopic data were reported in 2001 [2]. Following our recent report of the first generation of the parent 1,4-oxazine [3], we were interested to explore routes to the analogous 1,4-thiazine and many of these attempts have involved starting from 1, although we have so far been unable to reproduce the reported [1] direct reduction of 1 to 1,4-thiazine over aluminium powder.…”

Flash Vacuum Pyrolysis (FVP) of cis‐N‐phenyl‐hexahydro‐2H‐benzo[d][1,3]oxazin‐2‐imine and Thiazin‐2‐imine Derivatives

“…In addition, the proposed constrained asynchronous fragmentation that involves a ring contraction intermediate could explain the negative experimental Δ S # values for both compounds. This behavior is similar to the one reported for 1,4‐oxa(thia)zine‐diones ( 9 , 10 ) and oxazolidine‐diones ( 11 ) presented in Scheme 2 [30–31] …”

“…This result suggests an early loss of the heteroatom (O or S) to yield iminooxiranes which, in turn, extrude formaldehyde to yield nitriles as final products. The authors propose a mechanism consistent with the fragmentation path obtained by mass spectrometry of those heterocycles, Scheme 2 [30] . Oxazolidine‐2,4‐diones ( 11 ) also fragment under similar thermolysis conditions, showing a linked mechanism [31] …”