3-benzyliden-4-phenyl- 796 complex with

A series of new palladium complexes 26 bearing a phosphine-functionalised NHC ligand has been shown to be more efficient than typical catalytic systems (i.e. Pd(OAc), PPhj) for the reaction depicted in Scheme 7.10 [55], In fact, these conditions afforded the 9-benzylidene-97f-fluorene in higher yields when iodobenzene was used, whereas the reaction of the less reactive phenyl bromide with diphenylacetylene was achieved for the first time affording the desired product in moderate to good yields. 

Only a few reactions with bidentate ligands have been described. 32, reacting with the chiral carbohydrate derivative phenyl-4,6-o-(R)-benzylidene -2,3, 0-bis(diphenyl-phosphino-/ -D-glucopyranoside) (Ph-/ -glup), gave the compound [TcBr(CO)3 (Ph-/Tglup)] (56) in 53% yield. The complex was characterized by elemental analysis and i.r. spectroscopy [71]. Furthermore, reaction with dithio-... 

Carbohydrates remain an attractive source of chirality in preparation of ligands for asymmetric catalysis. Functionalized phospholanes, 192 [167], and chiral bisphosphinites 193 [168] with an attached crown ether unit were obtained recently from D-mannitol and from phenyl 2,3-di-0-allyl-4,6-0-benzylidene-p-D-glucopyranoside, respectively (Figure 18). Compounds 194 and 195 were obtained in the photochemical addition of H2P(CH2)3PPH2 onto the crresponding alkenes - Pd-complexes of these new bisphosphines were successfully applied as catalysts in the copolymerization of CO and... 

The first attempt to prepare 2-phenyl-4-(phosphoranylidene)-5(4//)-oxazolone 219 started with l-benzoylamino-(2,2-dichloroethenyl)triphenylphosphonium chloride 216 and involved the complex reaction sequence shown in Scheme 7.67. The structure and properties of 219 were studied and it was shown that 219 underwent Wittig olefination with benzaldehyde to give the well-known (Z)-4-benzylidene-2-phenyl-5(477)-oxazolone. ... 

Analogous reactions can occur with high-valent Nb and Ta complexes. . Reaction of Ta(CHCMe3)(OCMe3)2(PMe3)Cl with phenyl-substituted alkenes forms the corresponding benzylidene complexes ... 

Scheme 7.13 Decomposition of the ruthenium catalyst via the activation of the ortho C-H bond on the A/-phenyl group. Gibbs free energies in kcal mol with respect to the 14-electron ruthenium benzylidene complex are given in parentheses. Calculations were performed at the BP86/SDD-SVP level of theory with lEF-PCM solvation model (CHjClj solvent). Adapted from Ref [59].

Complexes of lithium aluminium hydride with l,4 3,6-dianhydro- and 1,3 4,6-di-O-benzylidene-D-mannitol, each of which contains a two-fold axis of symmetry, have been used to achieve asymmetric reductions of some alkyl aryl and dialkyl ketones e.g. methyl or ethyl phenyl ketone and 3,3-dimethylbutan-2-one). All reductions with lithium l,4 3,6-dianhydro-D-mannitolatodihydridoaluminate(iii), using a 2 1 molecular ratio of ketone to reducing agent, gave the 5-enantiomer of the secondary alcohol preferentially (selectivity 1.1—5.3 %), whereas those of alkyl aryl ketones and dialkyl ketones gave more of the 5- and R-alcohols, respectively, when lithium l,3 4,6-di-0-benzylidene-D-mannitolatodihydridoaluminate(iii) was used. 

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