Menthyl-substituted organophosphorus compounds. Part 6. Preparation of P(L-men)RCl and P(L-men)R(S)Cl (R = Me, Et, Pri, But, or Ph; men =cyclo-C6H9-2-Pri-5-Me) and nuclear magnetic resonance studies of configuration and halogen exchange

Abstract

Menthyl-substituted chlorophosphines P(L-men)RCl and thiophosphoryl chlorides P(L-men)R(S)Cl (R = Me, Et, or Prⁱ; men = menthyl, i.e. 2-isopropyl-5-methylcyclohexyl) have been prepared. These series (including compounds with R =Ph and Bu^t) were subjected to ¹H, ¹³C, and ³¹P n.m.r. studies at ambient temperature. Chemical shifts of C-4, C-8, H-8, CH₃-7, CH₃-9, and CH₃-10 and the coupling constants ²J_PC-2, ²J_PC-4, ³J_PC-1, and ³J_PC-8 are stereospecific indicators for the configurations of phosphorus in P-epimeric forms of P(L-men)R(S)Cl. The values of ²J_PC-2 and ²J_PC-4 reflect effects from intramolecular rotation around the P–C(menthyl) bond. Influences from substituents R on chemical shifts and coupling constants are discussed. Variable-temperature ³¹P n.m.r. studies using line broadening and selective inversion-recovery techniques on chlorophosphines P(L-men) PhCl and P(L-men) EtCl revealed halogen-exchange processes which are likely to have cationic phosphorus intermediates.