31082-06-1Relevant academic research and scientific papers
PHOSPHORORGANISCHE VERBINDUNGEN 92 Zur Stereochemie und zum chemischen Verhalten optisch aktiver Amidophosphoniumsalze und optisch aktiver Phosphinigsaereamide
Horner, Leopold,Jordan, Manfred
, p. 225 - 234 (2007/10/02)
Optically active amides of phosphinous acids R1R2PNR2 4 (R1 = Ph, R2 = Me, R = Et) may be obtained in high yield from the corresponding chiral amidophosphonium salts 1R2R3PNR2>X(R1 = Ph, R2 = CH3, Et, R3 = Bz or allyl, R = Et) via cathodic fassion or cyanolysis, both processes proceeding under retention of configuration at phosphorus.The optically active amidophosphonium salts (e.g. ethyl-methyl-phenyl-diethylamidophosphonium iodide 10 or benzyl-ethyl-phenyl-diethylamidophosphonium bromide 12 were prepared: a.) from the optically active tertiary phosphines (e.g.R-(+)-benzyl-methyl-phenyl-phosphine 6 or S-(-)-ethyl-methyl-phenyl-phosphine 13 on treatment with aryl or alkyl azides and subsequent alkylation of the ensueing phosphine imine 7. b.) from the chiral phosphinous acid amide 4 on alkylation.Methods a) and b) proceed under retention of configuration at phosphorus. c.) treatment of chiral phosphines with N-haloamines results in racemic amidophosphonium salts. Optically active amidophosphonium salts (eg.S-(+)-benzyl-methyl-phenyl-diethylamidophosphonium bromide 8 or R-(-) 10) are converted to the corresponding phosphine oxides 9 or 11 under inversion of configuration on treatment with aqueous alkali.LiAlH4 removes the amino ligand, converting amidophosphonium salts (eg.S-(+) 12) to the optically active phosphine under retention of configuration.Treatment of S(+)-ethyl-phenyl-diethylamidophosphonium bromide 5 with benzaldehyde gives stilbene and chiral ethyl-phenyl-phosphinic acid diethylamide 17 under retention of configuration; 7 is also obtained from R-(-) 4 on oxidation with H2O2.R-(-) 4 gives optically active ethyl-phenyl-thiophosphine acid diethylamide 18 on treatment with sulphur.Optically active 4 undergoes spontaneous racemization at 130 deg either in the neat phase or dissolved in hydrocarbons, zero order kinetics being observed.The racemization is proposed to occur through a cyclic bimolecular association, since compounds with different groups at phosphorus and nitrogen exchange ligands (forming crossed the phosphinous acid amides in approximately equal quantities) after three hours at 200 deg C.Phosphinous acid amides (eg. 4) form chiral charge-transfer complexes with nitrobenzene, which undergo racemization quickly even at room temperature.Optically active 4. when used as co-catalyst with (RhCl-hexa-1,5-diene), enables the homogeneous hydrogenation of α-ethylstyrene to 2-phenylbutane to be carried out with an optical yield of 34percent.
