14554-58-6Relevant academic research and scientific papers
Synthesis and conformational study of stereoisomeric 2-phenyl-4a,5,6,7,8,8a-hexahydro-4H-1,3,4-benzoxadiazines
Rosling, Ari,Fueloep, Ferenc,Askolin, Curt-Peter,Mattinen, Jorma
, p. 2237 - 2250 (2007/10/03)
The synthesis and conformational behaviour of some new cis- and trans-fused N4-R-2-phenyl-4a,5,6,7,8,8a-hexahydro-4H-1,3,4-benzoxadiazines are described. Their vicinal coupling constants reveal that the trans-fused isomers adopt an anancomeric chair-(half-chair) conformation, whereas the cis-fused isomers exist in a conformational equilibrium of the O-in (having the oxygen attached axially to the cyclohexyl ring) and O-out conformers. At room temperature, the O-in conformers slightly predominate, as estimated from the vicinal coupling constants. However, only a rough estimation, especially in the cis N-CH2Ph derivative 9a, can be made of the conformational equilibria due to an obvious deformation of the carbocyclic ring (a flattened, non-ideal chair conformation), making the selection of model 3JH,H values difficult. At 193 K the O-in conformer predominates in a ratio of 85:15 for the cis N-CH2Ph derivative and 70:30 for the cis N-Me derivative, estimated from the 13C signal integrals of both cis conformers, as they separated in low-temperature experiments (193 K).
