The complexes [Pt(CH3)Cl(P-P)] 1-3 (1, P-P = (S)-6,6′-(dimethoxybiphenyl)-2,2′-diylbis-(diphenylphosphine) ((S)-MOBIPH); 2, P-P = OR)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl ((R)-BINAP); 3, P-P = (2S,3S)-2,3-O-isopropylidene-2,3-dihydroxy-1,4-(diphenylphosphino)-butane ((S,S)-DIOP)) in the presence of SnCl2 catalyze the asymmetric hydroformylation of styrene. The reaction proceeds under mild conditions (50°C, P(H2) = P(CO) = 50 atm) to give the desired branched aldehyde with moderate regioselectivity. Good enantioselectivities (up to 75%) have been obtained using [Pt(CH3)Cl{(S)-MOBIPH}]. The influence of solvent, temperature, P(H2), and P(CO) has been studied. An impressive influence of the solvent has been observed: using [Pt(CH3)Cl{(R)-BINAP}], the chirality of 2-phenylpropanal obtained 3, in toluene or in tetrahydrofuran is opposite to that of 2-phenylpropanal produced in dichloromethane or acetone. Using [Pt(CH3)Cl{(S)-MOBIPH}] or [Pt(CH3)Cl{(R)-BINAP}], an unusual increase of the rate and enantioselectivity of the reaction with increasing P(CO) is observed. In order to get information on the reaction mechanism, the carbonylation of [Pt(CH3)(SnCl3){(S)-MOBIPH}] (4) has been studied. This reaction carried out at room temperature and atmospheric pressure affords an equilibrium mixture containing the cationic alkyl complex [Pt(CH3)(CO){(S)-MOBIPH}]+[SnCl3]- (6) and the neutral acyl species [Pt(COCH3)(SnCl3){(S)-MOBIPH}] (7). The carbonylation of [Pt(CH3)(SnCl3){(R)-BINAP}] (5) proceeds in the same fashion to give [Pt(CH3)(CO){(R)-BINAP}]+[SnCl3]- (8) and [Pt(COCH3)(SnCl3){(R)-BINAP}] (9).

Asymmetric hydroformylation of styrene catalyzed by platinum(II)-alkyl complexes containing atropisomeric diphosphines

SCRIVANTI, Alberto;BEGHETTO, Valentina;MATTEOLI, Ugo;
1996-01-01

Abstract

The complexes [Pt(CH3)Cl(P-P)] 1-3 (1, P-P = (S)-6,6′-(dimethoxybiphenyl)-2,2′-diylbis-(diphenylphosphine) ((S)-MOBIPH); 2, P-P = OR)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl ((R)-BINAP); 3, P-P = (2S,3S)-2,3-O-isopropylidene-2,3-dihydroxy-1,4-(diphenylphosphino)-butane ((S,S)-DIOP)) in the presence of SnCl2 catalyze the asymmetric hydroformylation of styrene. The reaction proceeds under mild conditions (50°C, P(H2) = P(CO) = 50 atm) to give the desired branched aldehyde with moderate regioselectivity. Good enantioselectivities (up to 75%) have been obtained using [Pt(CH3)Cl{(S)-MOBIPH}]. The influence of solvent, temperature, P(H2), and P(CO) has been studied. An impressive influence of the solvent has been observed: using [Pt(CH3)Cl{(R)-BINAP}], the chirality of 2-phenylpropanal obtained 3, in toluene or in tetrahydrofuran is opposite to that of 2-phenylpropanal produced in dichloromethane or acetone. Using [Pt(CH3)Cl{(S)-MOBIPH}] or [Pt(CH3)Cl{(R)-BINAP}], an unusual increase of the rate and enantioselectivity of the reaction with increasing P(CO) is observed. In order to get information on the reaction mechanism, the carbonylation of [Pt(CH3)(SnCl3){(S)-MOBIPH}] (4) has been studied. This reaction carried out at room temperature and atmospheric pressure affords an equilibrium mixture containing the cationic alkyl complex [Pt(CH3)(CO){(S)-MOBIPH}]+[SnCl3]- (6) and the neutral acyl species [Pt(COCH3)(SnCl3){(S)-MOBIPH}] (7). The carbonylation of [Pt(CH3)(SnCl3){(R)-BINAP}] (5) proceeds in the same fashion to give [Pt(CH3)(CO){(R)-BINAP}]+[SnCl3]- (8) and [Pt(COCH3)(SnCl3){(R)-BINAP}] (9).
1996
15
File in questo prodotto:
File Dimensione Formato  
Asymmetric hydroformylation of styrene catalyzed by platinum(II)-alkyl complexes containing atropisomeric diphosphines.pdf

non disponibili

Tipologia: Documento in Post-print
Licenza: Accesso chiuso-personale
Dimensione 233.75 kB
Formato Adobe PDF
233.75 kB Adobe PDF   Visualizza/Apri

I documenti in ARCA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10278/14058
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 18
  • ???jsp.display-item.citation.isi??? 17
social impact