Phosphonites and diphosphites derived from biphenanthrol for use in asymmetric catalysis.
ChapterI contains a review of phosphoniteisn asymmetric catalysis and recent
developments in asymmetric hydrogenation and a symmetric hydroformylation catalysis.
Chapter2 is concerned with new phosphonite ligands f r asymmetric catalysis.
A new three-steps ynthesiso f 9,9'-biphenanthryl-10,10'-dio(lb iphenanthrol') in 36%
yield from phenanthrene is reported. The ligands PhP(OR)2, PhP(OR')2,
(RO)2PCH2CH2P(OR)2a nd Ph2PCH2CH2P(OR)2 derived from 'biphenanthrol'
(HOR)2 and dimethyl-1,1'-binaphthyl-2,2'-dihydroxy-3,3'-dicarboxylate( HOR')2
have been synthesised and their Pt(O,I I) and R h(I) chemistry is discussed The crystal
structures of two complexes of the type [PtC12(phosphonite)h2a] ve been determined.
The monoPhosphonite, diphosphonite and phosphinophosphonite complexes
[Rh(cod)P2]BF4 derived from (S)-'biphenanthroal'r e described.
In Chapter 3, the chemistry of some new diphosphites is described. The
diastereomeric mixture of (RO)2P(ORRO)P(OR)2( 'biphenanthrite') is formed by
reacting (±)-'biphenanthrol' with PC13- Optically pure (R, R, R)-'biphenanthrite' is
similarly prepared from (R)-biphenanthrol'.The side-products and intermediates in
this reaction are identified by their independent syntheses C: IP(OR)2,H (O)P(OR)2,
(RO)2POP(OR)a2n d (HORRO)P(OR)2 Dehydration of 'biphenanthrola' lso occurs to
give a furan, which was characterisedb y X-ray crystallography. Two equivalents of
(R)-CIP(OR)2 react with (R)- or (S)-'binaphthol' (HOR")2 to give (R, R, R)- and
(R, S, R)-(RO)2P(OR"R"O)P(OR)2 ('pnp'). The disodium salt of (±)-'biphenanthrol'
reacts with two equivalents of (±)-CIP(OR)2 to yield the single ((R, SR) / (SR, S))-
diastereomeor f 'biphenanthriteT. he Pt(II), Pd(11aI)n dR h(I) coordinationc hemistry of
these new diphosphitesis reported. The complexes[ MC12(diphosphite)a] re fluxional
due to the conformational flexibility of the nine-memberech delate ring and the crystal
structures of (R,R ,R )- and (SR,S )-[PtC12('biphenanthrite)s]h ow very different ring
conformations T.he hydroformylation of styrenes catalysed by rhodium(I) complexes
of (R, R, R)-'biphenanthrite', (R, S, R)-'pnp' and (R, R, R)-pnp' is reported. The
'biphenanthritec' complex gives 50% branched aldehyde and no asymmetric induction.
The complex of (R, SR)-'pnp' gives 91-96% branched aldehyde and up to 72% ee.
The differences in the catalytic properties of the diastereomer is discussed.
In Chapter4 , the asymmetric hydrogenation of oc-enamides with rhodium(I)
complexes of the new phosphonites and diphosphitesa s catalysts is discussed The
diphosphonite complex shows low activity and a modest ee (up to 41%) but the
analogousp hosphinophosphonitceo mplex is highly active and gives high ee's (up to
88%).T his is the first phosphinophosphonittoe be used in asymmetric hydrogenation.
The monophosphonitceo mplexi s very activea ndt he ee's of up to 92% aret he highest
obtained with a monodentatleig and in asymmetric cc-enamide hydrogenation.
Chapter5 gives the experimental details for the chemistry reported in this thesis.