Efficient oxidative resolution of a P-stereogenic triarylphosphine and asymmetric synthesis of a P-stereogenic atropoisomeric biphenyl diphosphine dioxide

Racemic 3-methoxyphenyl(1-naphthyl)phenylphosphine 1 was effectively resolved via an oxidative resolution procedure utilizing l-menthyl bromoacetate as the resolving agent to give enantiopure 3-methoxyphenyl(1-naphthyl)phenylphosphine oxide (R)-2 in 41% yield. Reduction of the resolved (R)-4 with HSiCl3/NEt3 provided the corresponding phosphine (R)-1 in >97% ee. Ortho-iodination of the enantiopure (R)-4 followed by Ullmann coupling of the resulting iodoarylphosphine oxide gave a P-stereogenic and atropoisomeric biphenyl diphosphine dioxide as a single diastereoisomer. The latter transformation constitutes the first example of an effective transfer of a P-centered chirality to an axial chirality of the atropoisomeric biaryl system. The absolute configurations of the resolved phosphine and the atropoisomeric biaryl system have also been established.

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(2-Isopropyl-5-methylcyclohexyloxycarbonylmethyl)(3-methoxyphenyl)(naphthalen-1-yl)phenylphosphonium hexafluorophosphateC35H40F6O3P2[α]D = −6.0 (c 1.3, CHCl3)Absolute configuration: (SP)Source of chirality: l-menthyl bromoacetate

3-Methoxyphenyl(1-naphthyl)phenylphosphine oxideC23H19O2P[α]D = +3.2 (c 1.0, CH2Cl2)Absolute configuration: (SP)Source of chirality: l-menthyl bromoacetate

3-Methoxyphenyl(1-naphthyl)phenylphosphineC23H19OP[α]D = +3.1 (c 1.0, CH2Cl2)Absolute configuration: (RP)Source of chirality: l-menthyl bromoacetate

2-Iodo-3-methoxyphenyl(1-naphthyl)phenylphosphine oxideC23H18IO2P[α]D = −14.5 (c 1.0, CH2Cl2)Absolute configuration: (SP)Source of chirality: l-menthyl bromoacetate

(6,6′-Dimethoxybiphenyl-2,2′-diyl)bis(1-naphthyl) phenylphosphine oxideC46H36O4P2[α]D = +87.6 (c 0.5, EtOH)Absolute configuration: (Sa,SP,SP)Source of chirality: l-menthyl bromoacetate