Palladium complexes cyclohexenyl

X-ray and P NMR studies of (T -cyclohexenyl)palladium complex of 53 concluded that high enantioselectivity is due to the exclusive formation of an exo 7t-allylpalladium intermediate induced by the interaction between the 2-biphenylyl group and the Mn(CO)3 moiety. 

A multi-step asymmetric synthesis of a hydrindane framework was achieved in water via asymmetric allylic alkylation, propargylation and aquacatalytic cycloisomerization of a 1,6-enyne, where all three steps were performed in water with the recyclable polymeric catalysts. The racemic cyclohexenyl ester 27 reacted with diethyl malonate under the conditions mentioned in Table 6.1 to give 90-92% ee of 34b. The polymeric chiral palladium complex 23-Pd was reused four times... 

They observed that the larger the aryl group the faster the reaction proceeded. For example, the palladium complex of 65d catalysed the reaction of cyclohexenyl triflate 35 with... 

Structural information regarding the conformation of the 77 -allyl ligand in palladium complexes can be extracted from the analysis of H- H coupling constants from NMR spectra since they are related to the dihedral angles of vicinal protons according to the Karplus equation or improved expressions derived from it. The predominant boat- or ri /r-conformation of cyclohexenyl derivatives in solution can be ascertained according to Vh-h and Vh h values, which sometimes correspond to the averaged value of both conformations in fast equilibrium, J values have been calculated by application of molecular mechanics and they conform to the experimental values. The analysis of Vh-h... 

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. 

Palladium(O) or readily reduced paUadium(II) complexes were the most efficient catalysts, giving higher yields than analogous Pt catalysts. The Markovnikov product was formed with high regioselectivity. In dialkynes, both C=C bonds could be hy-drophosphorylated, while the C=C double bond in a cyclohexenyl alkyne subshtuent did not react. With trimethylsilylacetylene, unusual anti-Markovnikov selectivity was observed. 

In the above-mentioned preparation of the u-cyclohexenyl complex, [PdCliV-CeHglb, benzene and cyclohexane are formed. ThisTr-cyclohexenyl complex is also formed from cyclohexa-1,3-diene, either by treating it with sodium chloropalladite 191) or with palladium chlorocarbonyl, [PdCl2-(CO)]2 81, 88). 

Addition of dichloroketen to cyclohexenyl phenyl sulphoxide yields the ds-lactone (18). The methylbutanolide (19) is formed by the reaction of but-3-en-l-ol with carbon monoxide in the presence of palladium(II) chloride, copper(II) chloride, and triphenylphosphine. Palladium(0)-phosphine complexes catalyse the carboxylation of isopropylidenecyclopropane to give the furanone (20). ... 

The spectrum of a ir-allyl system where H has been substituted is often v ry simple but when substitution at or occurs considerably more complex spectra are observed. Nonetheless, the spectrum of 77-crotyl-palladium chloride can be interpreted satisfactorily on the basis of an AMM X system 16, 44). In some cyclohexenyl complexes of palladium, the hydrogens are substituted by a (—CH2—group. A comparison of their spectra with those of analogous rr-allyl complexes confirms the assignments of the H hydrogens to the higher doublet in the spectra of the unsubstituted complexes 33, 61, 99). In the case of the platinum complex... 

Competitive experiments of allyl phenyl sulfide and allyl phenyl selenide with this system indicate that oxidative addition of the organic selenide is faster. The equilibrium displacement between the allylic sulfide and 7 -allylic complex depends on the actual precursor for Pd(0) phosphine complexes (Equation (41)). The stereochemistry of the reverse reaction on 7/ -cyclohexenyl palladium thiolate dimers (nucleophilic attack of sulfide) has been determined to be trans. According to the principle of microscopic reversibility, the oxidative addition of allylic sulfides must occur with inversion of configuration. 

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