Phospholane-3-carboxylic acid

Esterification of hypophosphorous acid was achieved by reaction with tetraisopropyl orthosilicate 62, which, when treated with methyl acrylate 63, afforded the triester 65, which was cyclized to 66 in the presence of n-butyllithium. Selective hydrolysis of compound 66 with hydrochloric acid (3 M) in the presence of isopropyl alcohol gave, in moderate yield, the six-membered phosphaketone 67. The phospholane-3-carboxylic 68 was obtained fi om ring contraction mediated by thallium(in) along with oxidation reaction in one step. The carboxylic acid function... 

The enantioselective deprotonation of 128 and oxidative addition of the carbanion with Cu(II) afforded TangPhos disulfide as a mixture of diaster-eomers where the chiral C2-symmetric product was the major compound (66% de, 95% ee). A single recrystallisation afforded the desired optically pure TangPhos sulfide in 20% yield. The desulfuration was performed with hexa-chlorodisilane to yield the very air-sensitive Tangphos diphosphine in 88% yield. The synthesis of a family of phospholane-oxazoline ligands started with the preparation of carboxylic acid 129 by the proeedure in 40% yield after recrystallisation. The crude product was obtained in relatively low optical... 

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