Palladium complexes preparation

The water-soluble palladium complex prepared from [Pd(MeCN)4](Bp4)2 and tetrasulfonated DPPP (34, n=3, m=0) catalyzed the copolymerization of CO and ethene in neutral aqueous solutions with much lower activity [21 g copolymer (g Pd) h ] [53] than the organosoluble analogue in methanol. Addition of strong Brpnsted acids with weakly coordinating anions substantially accelerated the reaction, and with a catalyst obtained from the same ligand and from [Pd(OTs)2(MeCN)2] but in the presence of p-toluenesulfonic acid (TsOH) 4 kg copolymer was produced per g Pd in one hour [54-56] (Scheme 7.16). Other tetrasulfonated diphosphines (34, n=2, 4 or 5, m=0) were also tried in place of the DPPP derivative, but only the sulfonated DPPB (n=4) gave a catalyst with considerably higher activity [56], Albeit with lower productivity, these Pd-complexes also catalyze the CO/ethene/propene terpolymerization. 

Fig. S. Diagrams of the halogenomethyl palladium complexes prepared by McCrindle el al. [Adapted with permission from the American Chemical Society, Elsevier Sequoia S. A., and the Royal Society of Chemistry from R. McCrindle, G. Ferguson, G. J. Arsenault, A. J. McAlees, B. L. Ruhl, and D. W. Sneddon, Organometallics 5,1171 (1986) R. McCrindle and D. W. Sneddon, J. Organomet. Chem. 282, 413 (1985) R. McCrindle, G. J. Arsenault, R. Farwaha, A. J. McAlees, and D. W. Sneddon, J. Chem. Soc., Dalton Trans., 761 (1989).]...

In addition, Durand et al. have recently used an axially chiral monodentate phosphine, such as (I j-Ph-BINEPINE (Scheme 2.62), as a chiral resolving agent of a racemic palladium complex prepared from a 2-ferrocenyl-l,10-phenanthroline ligand. The reaction evolved through a DKR process, leading after recrystallisation to the isolation of only one of the two possible diastereoisomers. 

An interesting regiochemistry has been observed in the palladium-catalyzed allylic alkylation of ( )-3-substituted-2-propene acetate and 1-substituted 2-propenyl acetate. In this allylic substitution catalyzed by a palladium complex prepared from 1 in the presence of (/ )-MeO-MOP catalyst (P/Pd = 2/1), a selective substitution at the position originally substituted with acetate was observed (eq 62). Studies with 3-deuterio-2-cyclohexenyl acetate revealed that neutral phosphane Pd-complex is formed during the process. 

Seven procedures descnbe preparation of important synthesis intermediates A two-step procedure gives 2-(HYDROXYMETHYL)ALLYLTRIMETH-YLSILANE, a versatile bifunctional reagent As the acetate, it can be converted to a tnmethylenemethane-palladium complex (in situ) which undergoes [3 -(- 2] annulation reactions with electron-deficient alkenes A preparation of halide-free METHYLLITHIUM is included because the presence of lithium halide in the reagent sometimes complicates the analysis and use of methyllithium Commercial samples invariably contain a full molar equivalent of bromide or iodide AZLLENE IS a fundamental compound in organic chemistry, the preparation... 

The original Sonogashira reaction uses copper(l) iodide as a co-catalyst, which converts the alkyne in situ into a copper acetylide. In a subsequent transmeta-lation reaction, the copper is replaced by the palladium complex. The reaction mechanism, with respect to the catalytic cycle, largely corresponds to the Heck reaction.Besides the usual aryl and vinyl halides, i.e. bromides and iodides, trifluoromethanesulfonates (triflates) may be employed. The Sonogashira reaction is well-suited for the synthesis of unsymmetrical bis-2xy ethynes, e.g. 23, which can be prepared as outlined in the following scheme, in a one-pot reaction by applying the so-called sila-Sonogashira reaction ... 

Unsymmetrical oc-diketones RCOCOR have been prepared by treatment of an acyl halide RCOCl with an acyltin reagent R COSnBus, with a palladium complex catalyst. 

A number of methods, all catalyzed by palladium complexes, have been used to prepare unsymmetrical biaryls (see also 13-14). In these methods, aryl bromides or... 

Sparteine 1 was also used in a palladium complex-catalyzed enantios-elective benzoylation of alcohols using monoxide and the organobismuth(V) compound (Scheme 37). The carbonylative acylation of alcohols using carbon monoxide (CO) is known to be an alternative tool for the prepar-... 

Helquist et al. [129] have reported molecular mechanics calculations to predict the suitability of a number of chiral-substituted phenanthrolines and their corresponding palladium-complexes for use in asymmetric nucleophilic substitutions of allylic acetates. Good correlation was obtained with experimental results, the highest levels of asymmetric induction being predicted and obtained with a readily available 2-(2-bornyl)-phenanthroline ligand (90 in Scheme 50). Kocovsky et al. [130] prepared a series of chiral bipyridines, also derived from monoterpene (namely pinocarvone or myrtenal). They synthesized and characterized corresponding Mo complexes, which were found to be moderately enantioselective in allylic substitution (up to 22%). 

In preparing this chapter, the authors surveyed a vast literature seeking studies with original findings, convincing explanations, and probable useful applications. Merely solid studies were downplayed, as their results are more or less predictable. Whenever possible, studies of palladium complexes were placed in their broader context, with minimal dilution of the content of this chapter. 

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