6533b7d3fe1ef96bd1261185

RESEARCH PRODUCT

Ligands P-stéréogéniques dérivés du calix[4]arène. Synthèses et applications en catalyse asymétrique

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We were interested in synthesis of P-stereogenic ligands derived from calix[4]arene and in their application in asymmetric catalysis. Mono et diphosphines were prepared on the upper rim of the macrocyle starting from the mono or dianion of the calix[4]arene and chlorophosphines borane or the oxazaphospholidine borane complex. The best selectivity was obtained by reaction of the dianion with the oxazaphospholidine borane complex leading to a bisaminophosphine borane. After acidolysis with HCl giving the corresponding bischlorophosphine and reaction with organolithium reagents, diphosphines diborane were obtained with good yields (40 à 60 %). X-ray structures of the prepared ligands confirmed the stereospecificity of the ephedrine method. Preparation of P-stereogeniques diphosphines elevated above the upper rim of the calix[4]arène was carried out by reaction of phosphides borane with the corresponding bisiodomethyl derivative. Ligands aminophosphinephosphinite (AMP*P) were also prepared from the opened product of the oxazaphospholidine borane complex by the calixarene anion.Ligands were synthetised in borane complex serie. Decomplexation with DABCO affords quantitatively the free phosphanes which were used in the preparation of transition metal catalysts. AMP*P bearing calix[4]arene on the aminophosphine moeity gave very high asymetric induction in hydrogenation catalysis of methyl α-acetamidocinnamate with rhodium complexes (98% e.e.). Compared study with isoelectronic or sterically similar ligands obviously prove the positive influence of the calix[4]arene substituent. P-stereogenic mono and diphosphines on the upper rim of the macrocycle were used in asymetric allylic subtitution catalyzed with palladium complexes. High yields and enantioselectivities were obtained with carboned and nitrogened nucleophiles. The best inductions were carried out with a diphosphine bearing methyl and phenyl on the phosphorous centers, affording enantiomeric excesses of 82 % and 79 % in alkylation and in amination, respectively.