115410-90-7Relevant articles and documents
Cycloadditions of 6H-1,3,4-Oxadiazin-6-ones (4,5-Diaza-α-pyrones), 10. - Reactions of Bicyclohexenes with 6H-1,3,4-Oxadiazin-6-ones and Dynamic Effects in a Nine-Membered, Bridged, α,β-Unsaturated Enol Lactone
Reuchlein, Horst,Kraft, Arno,Christl, Manfred,Peters, Eva-Maria,Peters, Karl,Schnering, Hans Georg von
, p. 1435 - 1444 (2007/10/02)
The reactions of bicyclohexene (2) and its tricyclic derivative 3 with 2,5-diphenyl-6H-1,3,4-oxadiazin-6-one (1a) gave the 3,4-dihydro-α-pyrones 6 and 7, respectively.In contrast, the methyl phenyloxadiazinocarboxylate 1b and 2 afforded a mixture of the nine-membered, bridged, α,β-unsaturated enol lactone 11 and the β-lactone 12 in a ratio of about 10:1.Olefin 3 reacted with 1b to furnish small amounts of the bridged derivative 16 of 11 as well as the 2:1 product 14, a saturated δ-lactone.Unlike 16, enol lactone 11 reveals dynamic phenomena, which have been investigated by means of line shape analyses of the temperature depen dent 13C-NMR spectra.The interconvertion of the cis- and trans-lactone conformers (11a 11b), being present in a 1:2 ratio, proceeds with ΔHc,t(excit.) = 48.8 kJ mol-1, whereas the racemization of the trans-lactone enantiomers (11b 11b') requires less activation (ΔHt,t(excit.) = 42.3 kJ mol-1).The structure of cis-lactone 11a has been established by an X-ray analysis.
