Palladium 1-octene

A highly diastereoselective alkcnylation of c/s-4-cyclopentene-l,3>diols has been achieved with 0-protected (Z)-l-iodo-l-octen-3-ols and palladium catalyst (S. Torii, 1989). The ( )-isomers yielded 1 1 mixtures of diastcrcomcric products. The (Z)-alkenylpalladium intermediate is thought to undergo sy/i-addition to the less crowded face of the prochiral cyclopentene followed by syn-elimination of a hydropalladium intermediate. 

In examination of various disubstituted cyclic olefins, the following decreasing isomerization order was adduced Pd Rh, Ru, Pi > Os > r 84). At 20% conversion of 1-octene to octane, the ratio of isomerization to hydrogenation in isopropanol for various unsupported metals was Pd (2.05), Rh (0.125), Ru (0.121. Pt (0.025), Ir (0.025), Os (0.009) 82). Palladium is used frequently when migration and isomerization are wanted platinum, when they are to be avoided (2J24). 

Chitosan (Fig. 27) was deposited on sihca by precipitation. The palladium complex was shown to promote the enantioselective hydrogenation of ketones [80] with the results being highly dependent on the structure of the substrate. In the case of aromatic ketones, both yield and enantioselectiv-ity depend on the N/Pd molar ratio. Low palladium contents favored enan-tioselectivity but reduced the yield. Very high conversions were obtained with aliphatic ketones, although with modest enantioselectivities. More recently, the immobilized chitosan-Co complex was described as a catalyst for the enantioselective hydration of 1-octene [81]. Under optimal conditions, namely Co content 0.5 mmolg and 1-octene/Co molar ratio of 50, a 98% yield and 98% ee were obtained and the catalyst was reused five times without loss of activity or enantioselectivity. 

The preparation of N-carbethoxy-8-azabicyclo [5.1.0] oct-3-ene (158) from ethyl azidoformate (157) and 1,4-cycloheptadiene through a photolytic reaction, and its palladium(II)-catalyzed multistep rearrangement to N-carbethoxynortropidine (159), has been presented by Wiger and Retting as a new route to the 8-azabicyclo[3.2.1]octene skeleton (87) (Scheme 8). 

Huntsman et al. (62) hydrogenated optically active (- )-3,7-dimethyl-1-octene on a palladium catalyst and obtained a saturated product which was in part racemic. When the reaction was interrupted (50% completion) the 2,6-dimethyloctane isolated was only 7% racemized,... 

Poly(ethylene oxide) polymers and poly(ethylene oxide/propylene oxide) copolymers with iminodipropionitrile (139) or iminodiacetonitrile end groups were used as ligands in the palladium-catalyzed oxidation of higher olefins (1-octene to 1-hexadecene) at 50-70 °C with atmospheric air or 1-3 bar O2. In an ethanol/water mixture 88 % yield of 2-hexanone and 92 % yield of 2-hexadecanone was obtained in 4 and 2 h, respectively, with a... 

The H-P bond in hydrogen phosphonates readily adds across a C=C bond [22]. Upon treatment of 1-octyne with dimethyl phosphonate in the presence of a palladium complex in refluxing tetrahydrofuran, the addition reaction proceeds smoothly to afford dimethyl l-octen-2-ylphosphonate (2) regio-and stereo-selectively (Scheme 18). 

A solution of the above octene (50 g) in 100 ml of ethanol is shaken under 2-3 atmospheres of hydrogen in the presence of 0.6 g of 10% palladium-carbon catalyst, until no more hydrogen... 

Die Reaktion von Brom-ethen Oder 2-Brom-propen mit 1-Hexen und Morpholin oder Piperidin in Gegenwart von Palladium-acetat und (bei Verwendung von Morpholin) einem Triarylphosphan bei 100° ergibt 1-Morpholino- bzw. l-Piperidino-2-octene neben geringen Mengen an Octadienen1. 

Initial studies showed that the encapsulated palladium catalyst based on the assembly outperformed its non-encapsulated analogue by far in the Heck coupling of iodobenzene with styrene [7]. This was attributed to the fact that the active species consist of a monophosphine-palladium complex. The product distribution was not changed by encapsulation of the catalyst. A similar rate enhancement was observed in the rhodium-catalyzed hydroformylation of 1-octene (Scheme 8.1). At room temperature, the catalyst was 10 times more active. For this reaction a completely different product distribution was observed. The encapsulated rhodium catalyst formed preferentially the branched aldehyde (L/B ratio 0.6), whereas usually the linear aldehyde is formed as the main product (L/B > 2 in control experiments). These effects are partly attributed to geometry around the metal complex monophosphine coordinated rhodium complexes are the active species, which was also confirmed by high-pressure IR and NMR techniques. 

Palladium(II) chloride (Johnson Matthey) and 10% Pd/C (Aldrich) were used as received. Bis[(methallyl)chloropalladium(II)] (ref. 8), bis(dibenzylideneacetone)palladium(0) (ref. 9), metho-xyoctadienes (ref. 10), l-methoxy-3-octene (ref. 11), methoxyallyle and cis + traru-methoxycrotyle (ref. 12) were prepared as described in the literature. 

However, the platinum-t-butyl peroxide complex [lh(CF,C02)2(00But)(But0H)]2 selectively transforms terminal alkenes (e.g. 1-octene) into the corresponding methyl ketone,220 but much less efficiently than the palladium complex (23).42 This reaction becomes slightly catalytic in the presence of excess TBHP. 

Scheme 2 Two industrial processes involving a palladium-catalyzed telomerization step the production of 1-octanol by Kuraray (left) and 1-octene by Dow Chemical (right)...

Selectivity of the type found with ruthenium was not possible when palladium catalysts were used. For instance, hydrogenation of a mixture of 1- and 2-octene was completely nonselective over palladium catalysts. This lack of selectivity resulted from the high isomerization activity of palladium when the reaction was stopped at only one-tenth of completion, all 1-octene had disappeared by migration of the terminal double bond inward. 

Unhindered simple olefins are usually rapidly hydrogenated under very mild conditions over platinum metal catalysts such as platinum, palladium, and rhodium as well as over active nickel catalysts such as Raney Ni, nickel boride, and Urushibara Ni. For example, 0.1 mol of cyclohexene is hydrogenated in 7 min over 0.05 g of Adams platinum oxide in ethanol at 25°C and 0.2-0.3 MPa H2 (eq. 3.1).5 1-Octene and cyclopentene (eq. 3.2) are hydrogenated in rates of 11.5 and 8.6 mmol (258 and 193 ml H2 at STP) g Ni 1-min 1, respectively, over P-1 Ni in ethanol at 25°C and 1 atm H2.18 Hydrogenation of cyclohexene over active Raney Ni proceeds at rates of 96-100 ml H2 at STP (4.3-4.5 mmol) g Ni min-1 in methanol at 25°C and 1 atm H2 49,50 and can be completed within a short time, although usually larger catalyst substrate ratios than required for platinum catalyzed hydrogenations are employed (eq. 3.3).50... 

In a patent dealing with the selective hydrogenation of alkynols, use of palladium catalysts in combination with lower aliphatic amines such as butylamine, ethanolamine, and ethylenediamine, or in liquid ammonia was claimed to be more effective than use in the presence of higher amines, and superior to Lindlar catalyst in both activity and selectivity.43 Thus, linalool was obtained almost quantitatively by hydrogenation of 3,7-dimethyl-6-octen-l-yn-3-ol over Pd-CaC03 in the presence of butylamine (eq. 4.13). 

M. Green, J. A. K. Howard, J. L. Spencer, and F. G. A. Stone, Synthesis of Ethylene, Cyclo-octa- 1,5-diene, Bicyclo [2.2.1]heptene, and trans-Cyclo-octene Complexes of Palladium ) and Platinum(O) Crystal and Molecular Structure of Tris(bicyclo2.2.1]hepte-ne)platinum, J. Chem. Soc., Dalton Trans. 1977, 271-277. 

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