Benzene-, chloro palladium

Hydrogenation of 5-chloro-3-methy 1-6-phenyl-1,2,4-triazine (73) in benzene over palladium in the presence of triethylamine afforded the dechlorinated product (74) <85H(23)2807). The reduction of chloro-l,2,4-triazines, mainly by catalytic means, has been used for the synthesis of a variety of 1,2,4-triazines <76CB 1113 >. 

Telomerization of Isoprene.—Reviews have appeared on isoprene and chloro-prene, and on the complex reactions of isoprene to form terpenoids (in Japanese). Isoprene reacts with magnesium, especially in the presence of Lewis acids, and the resulting complex gives adducts with aldehydes. As usual in this type of reaction, a very complex mixture is obtained. The palladium-chloride-catalysed reaction of isoprene with acetic acid gives different products in different solvents. Monomers predominate in benzene [2-methylbut-2-enyl acetate (5) and 3-methylbut-2-enyl acetate (6)] while dimers [(7), (8), neryl (9), and geranyl (10) acetates] tend to be formed in tetrahydrofuran. Further details of the synthesis of Cio alcohols from isoprene and naphthyl-lithium are available, as well as of the in situ oxidation,but there is little of novelty (see Vol. 1, p. 17). 

Di-/z-chloro-bis[(1 -ethyl-2-methyl-Ji-allyl) palladium], like most alkyl- and aryl-substituted 7r-allylchloropalladium dimers, is a yellow, crystalline, air-stable solid, which is soluble in organic solvents of medium polarity (acetone, dichloromethane, chloroform, benzene). The reactions of these compounds have been described in several reviews.17... 

Preparation. - Fluorophosphines have been obtained from the reactions of the related chlorophosphines with trimethyl tin fluoride. Phenyl(isopropyl)-fluorophosphine has been resolved via a chiral amine-palladium(II) complex, providing the first example of the resolution of a free fluorophosphine chiral at phosphorus. This compound racemises at 20 °C in benzene solution over six hours. The neat compound rapidly decomposes by redox disproportionation. The same approach has been used for the resolution of the related chloro-phosphine, but the optically active compound could not be liberated unchanged from the crystallised diastereoisomeric palladium complex. The dihalo-genophosphines... 

The reactions of trifluoromethylthiosilver with cobalt- (p. 326), palladium-, or platinum-halogen compounds (p. 341) have already been discussed." The reaction of silver(i) oxide with (CFg)2S(0) NH and with CFa SOg NH SOjF in benzene provides a route to silver bis(trifluoro-methyl)sulphur oxyimine [(CFg)2S(0) NAg] and CF3-S0g-NAgS02F, respectively. Each gives the A methyl compound on treatment with methyl iodide, and (CF8)3S(0) NAg is readily converted into the iV-chloro-com-pound by chlorine. ... 

All lation of palladium(II)-coordinated phosphane ligands with l,2-bis(chloro-methyl)benzene gives rise to new chelate rings and coincidentally to the macrocyclic complex [Pd(L1216)](HC03)2 (Eq. 5.5). 

C5 3H1,7ClP2Pt, trans-Chloro isopropenylacetylido)bis(triphenylphos-phine)platinum II) - benzene (1 2), 43B, 1033 C5 3Hfl 7Cl3CuN202P2Pclf 2-(Chlorobis(triphenyIphosphine)palladium)-3-methyl-1,4-bis(methoxyphenyl)-1,4-diaza-butadien-1,4-diyl-dichloro-copper, 46B, 831... 

Di-M-chloro-di-7r( -chloroally)-dipalladium(II) is prepared via the reaction of allene with dibenzonitrile palladium dichloride in benzene (2-10). 1-Methyl- and 1,1-dimethyl-allene also can be used. With benzonitrile as a solvent, only the second product is obtained. 

Solvent effects on, and products from, reaction of styrene with ethylene in the presence of di-)ti-chloro-dichlorobis(styrene)dipalladium(n), [Pd-(Ph CH—CH2)Cl2]2, indicate a mechanism similar to (i)->(iv) above, with the addition of a preliminary equilibrium between the dimer and solvated monomers. The mechanism of reaction of styrene with vinyl compounds, catalysed by the same chloride-bridged dipalladium complex, has been studied using isotopic tracer (H, D) experiments. Palladium-acetate-catalysed reaction of styrene with benzene, also investigated using deuterium tracer experiments, involves no hydride shift, in contrast to the rather closely related Wacker process. The importance of intermediates with palladium-carbon n-bonds in palladium(ii)-catalysed alkylation and arylation of alkenes has been demonstrated. 

Senn and Ziegler find the dissociative pathway to be the preferred one in their calculations in THF solution of the oxidative addition of chloro-, bromo- and iodobenzene to Pd(P-P) complexes, where P-P is a chelating diphosphine ligand of the type l,2-bis(dimethylphosphino)ethane or (P)-2,2 -bis(dimethylphosphino)-1,1 -biphenyl. The barriers from the prereaction complex are in fact quite low 31, 12 and 5 kJ/mol for the chloro, bromo and iodo species, respectively. For methyl-(lS,5R)-5-chlorocyclohex-3-ene-l-carboxylate in presence of neutral palladium, Espinet and Echavarren observed retention of configuration in apolar solvent (benzene) and inversion in polar solvent (acetonitrile) [13]. 

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