First 1H NMR observation of chair–boat conformers in bispidinone system. Molecular structure of 3,7-diisopropyl-1,5-diphenyl-3,7-diazabicyclo-[3.3.1]nonane-9-one

Bispidine Coordination Chemistry

“…In solution, the measurement of dipole moments has led to the assumption that these compounds undergo a fast interconversion between the degenerate cb and bc conformations (154). This is confirmed by variable temperature 1 H-and 13 C NMR experiments (94,152,154). The small activation barrier for the chair-toboat interconversion is also of importance for the coordination of bispidine-type ligands to metal ions (see Section III).…”

“…Compounds with pyramidal nitrogen atoms (e.g., 49, 50-54, 65b or their diisopropylsubstituted analogues), tend to adopt a cb form in the solid. This is attributed to the phenyl groups, which prevent a flattening of the wings to some extent, because they do not allow a significant increase of the angles around C1 and C5, and therefore lead to a severe N Á Á ÁN repulsion (76,93,94,(150)(151)(152)(153). In solution, the measurement of dipole moments has led to the assumption that these compounds undergo a fast interconversion between the degenerate cb and bc conformations (154).…”

Fragmentation of 3,7-dialkyl-1,5-diphenyl-3,7-diazabicyclo[3.3.1]nonan-9-ones under electron ionization

“…Stability of this ion may be accounted for by the benzylic position of the positive charge. Alternatively, a [1,2]-sigmatropic hydrogen shift can yield an isomeric ammonium structure (Scheme 1). Elimination of a C 8 H 7 moiety (styrene radical) from ion D' gives rise to fragment G, which similarly to E possesses the charge in the benzylic position or isomerizes to an ammonium structure via a [1,3]-sigmatropic hydrogen shift.…”

“…2 A wide range of bispidines have been recently investigated as new biologically active compounds. 3 In particular, 1,5-diphenylbispidin-9-ones have shown properties as local anaesthetics.…”

The mannich reaction in the synthesis of N,S-containing heterocycles 4. Aminomethylation of 6-amino-3,5-dicyano-1,4-dihydropyridine-2-thiolates: A convenient regioselective route to 3,5,7,11-tetraazatricyclo[7.3.1.02,7]tridec-2-ene derivatives

“…To optimize the reaction conditions, we doubled the amount of the starting amine; as the result, the yields of tricyclic compounds 2 were increased to 66-95% (Scheme 1). 20 It should be noted that DABCN derivatives are of both theoretical (because of their peculiar confor mational structures) 21 and practical interest due to the specific ability to form strong complexes with transition metal cations 22 and a broad spectrum of biological activ ity inherent in bispidines. 19,20,22,23 In the reactions with thiolates 1, the formation of a bispidine like structure was unexpectedly accompanied by parallel cyclocondensation resulting in closure of a tetrahydro 1,3,5 triazine ring.…”