Biphospholes synthesis

Bromo-capped biphosphole (8b) is also the precursor of cychc derivatives, as illustrated by the synthesis of the fully unsaturated macrocycle (11), via a Wittig reaction involving the 5,5 -bis(carboxaldehyde) (10) (Scheme 2) [22]. An X-ray diffraction study revealed that macrocycle (11) is distorted, with an flZZ-trans-disposition of the four P-phenyl substituants. 

An excellent example of the use of method (2) for the synthesis of phospholyl complexes is given by the preparation of the Ca and Sr complexes 299 and 300. Here, insertion of either of these two metals into the P-P bond of 1,1 -biphosphole 298 occurs readily, affording the corresponding group 2 metal complexes (Scheme 102) <1999IC3207>. 

The reaction has been extended to the synthesis of a 2,2 -biphosphole <86iOM(3l6)27l>. The biphospholene derivative (249) is directly available from the reductive dimerization of phospholes <84JA425>. Addition of bromine gave the salt (250) which on dehydrohalogenation with a-picoline gave the biphosphole (251) (Scheme 71). 

Tissot O, Gouygou M, Dallemer F, Daran JC, Balavoine GGA (2001) New rhodium(l) and iridium(I) complexes of the chiral l,l -diphenyl-3,3, 4,4 -tetrameihyl-2,2 -biphosphole ligand—synthesis and applications to catalytic hydrogenation and hydroframylation reactions. Eur J Inorg Chem 2385... 

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