NMR study of spirophosphoranes derived from 2-aminophenols

Structural studies of spiroarsoranes derived from 2-aminophenols

“…The chemical shift of C5 is characteristic of heterocyclic systems with annular strain [4,6,[11][12][13]. Similarly, the chemical shift of C4 is also attributed to angular strain of the cyclic system and the planar trigonal geometry of the N atoms to which they are bonded [4,6,[11][12][13]. There are not published data of 15 N NMR of spiroarsoranes, however, the chemical shifts of N nuclei for 5-7 [δ = − 305.2 to − 301.8 ppm] are similar to spirophosphoranes derived from 2-aminophenols [6].…”

“…13 C NMR data of 5-7 in Table 2 show that the chemical shifts of C5 (bonded to O) and C4 (bonded to N) are similar to those analogue spirophosphoranes [4,11]. The chemical shift of C5 is characteristic of heterocyclic systems with annular strain [4,6,[11][12][13]. Similarly, the chemical shift of C4 is also attributed to angular strain of the cyclic system and the planar trigonal geometry of the N atoms to which they are bonded [4,6,[11][12][13].…”

“…Similarly, the chemical shift of C4 is also attributed to angular strain of the cyclic system and the planar trigonal geometry of the N atoms to which they are bonded [4,6,[11][12][13]. There are not published data of 15 N NMR of spiroarsoranes, however, the chemical shifts of N nuclei for 5-7 [δ = − 305.2 to − 301.8 ppm] are similar to spirophosphoranes derived from 2-aminophenols [6]. Therefore, these chemical shifts suggest that N atoms tend to have trigonal geometries.…”

“…Therefore, these chemical shifts suggest that N atoms tend to have trigonal geometries. The coupling constants 1 J ( 15 N-1 H) are in agreement with sp 2 hybridation of the nitrogen atom [ 1 J ( 15 N-1 H) = 88.6-90.2 Hz] and corroborate the trigonal geometry of the nitrogen atoms and its equatorial position in TBP spiroarsoranes [6].…”

“…In comparison with the spirophosphoranes, the structural studies of spiroarsoranes are scarce. For example, it has been mentioned in spirophosphoranes that the phosphorus atoms adopt TBP geometries with the better electrodonor substitutes in equatorial positions; N atoms adopt trigonal geometries and exist N-P retrocoordination due to d π − p π interaction [4][5][6][7]. However, N-As retrocoordination phenomena are less feasible in arsoranes due that the high energy of the 4d orbitals of As make little probable their participation in π bonds with N atoms.…”