New chiral P-ligands: P-amino- and P-cycloalkoxy dibenzo[c.e][1,2]oxaphosphorines

The reaction of racemic chloro-dibenzo[c.e][1,2]oxaphosphorine with (S)-(−)-α-methyl-benzylamine and (1R,2S,5R)-(−)-menthol led to a mixture of optically active diastereomers of the corresponding phosphonous derivatives. The isomers were separated in a diastereomeric excess of 71–93% at the phosphonic oxide and/or at the phosphonous borane stage. The P(III) boranes are suitable precursors of the P-ligands. The absolute P-configuration in one of the menthyl phosphonates isolated was determined by single crystal X-ray analysis.

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(6R)-6-(1R,2S,5R)-(−)-Menthyl-dibenzo[c.e][5,6]oxaphosphorineC22H27O3PDe = 78%[α]D25=-19.8 (c 1.0, CHCl3)Source of chirality: separation of optically active diastereomersAbsolute configuration: (6R)-6-(1R,2S,5R)

(6S)-6-(1R,2S,5R)-(−)-Menthyl-dibenzo[c.e][5,6]oxaphosphorineC22H27O3PDe = 71%[α]D25=-41.7 (c 1.0, CHCl3)Source of chirality: separation of optically active diastereomersAbsolute configuration: (6S)-6-(1R,2S,5R)