Cycloocta-1,5-dienes, substituted

The previously reported4 procedure, which is a technique of general utility, involves the reaction of dichloro(l,5-cycloocta-diene)palladium(II) with a solution of sodium bromide in acetone. The following procedure gives comparable yields and eliminates the need for the preparation of the dichloro intermediate. Bicyclo[2.2.1]hepta-2,5-diene (2,5-norbornadiene) may be substituted in the following procedure for the 1,5-cyclooctadiene to yield (bicyclo[2.2.1]hepta-2,5-diene)dibromopalladium(II). 

Nickel(O) or palladium(II) compounds in stoichiometric amounts promote the ring enlargement of simple alkyl-substituted 1,2-divinylcyclobutanes in benzene at room temperature to give 1 1 metal complexes of cycloocta-1,5-dienes.119 Destruction of the palladium complexes with potassium cyanide affords the free cycloocta-1,5-dienes. The stereochemistry observed is the same as in the thermal reaction at 150°C. 

There have been reports of syntheses of cyano complexes in fused potassium cyanide, though the characterization of the products has not always been satisfactory.1 The dry reaction between potassium cyanide and potassium hexaiodoplatinate(IV), however, certainly gives the impure hexacyano-platinate(IV) and substitution of cycloocta-1,5-diene bonded to platinum(II) may be achieved by the use of solid potassium cyanide in the presence of a crown ether catalyst.16... 

Cyclic allenes are the subject of considerable interest as strained unsaturated cyclic compounds168-170. lerl-Butyl-substituted cycloocta-1,2-diene is known as the smallest isolable cyclic allene170,171. Seven- and six-membered cyclic allenes are also well known as important intermediates in organic synthesis, and many synthetic methods have been... 

Substituted cycloocta-1, 5-diene complexes of CpCO and CpRh. (MW). 

Using a relative rate method, rate constants for the gas-phase reactions of O3 with 1- and 3-methylcyclopentene, 1-, 3- and 4-methylcyclohexene, 1-methylcycloheptene, cw-cyclooctene, 1- and 3-methylcyclooctene, cycloocta-1,3- and 1,5-diene, and cyclo-octa-l,3,5,7-tetraene have been measured at 296 2 K and atmospheric pressure. The rate constants obtained (in units of 10-18 cm3 molecule-1 s-1) are as follows 1-methylcyclopentene, 832 24 3-methylcyclopentene, 334 12 1-methylcyclohex-ene, 146 10 3-methylcyclohexene, 55.3 2.6 4-methylcyclohexene, 73.1 3.6 1-methylcycloheptene, 930 24 d.s-cyclooclcnc, 386 23 1-methylcyclooctene, 1420 100 3-methylcyclooctene, 139 9 d.v.d.v-cycloocta-1,3-diene, 20.0 1.4 cycloocta- 1,5-diene, 152 10 and cycloocta-l,3,5,7-tetraene, 2.60 0.19 the indicated errors are two least-squares standard deviations and do not include the uncertainties in the rate constants for the reference alkenes (propene, but-l-ene, d.s-but-2-ene, trans-but-2-ene, 2-methylbut-2-ene, and terpinolene). These rate data were compared with the few available literature data, and the effects of methyl substitution have been discussed.50... 

The reaction conditions are similar to those employed in the diacetoxylation reaction, with the difference that the halide concentration (usually CI ) has been increased. Thus, palladium-catalyzed oxidation of 1,3-dienes with / -benzoquinone in the presence of lithium chloride and lithium acetate gives l-acetoxy-4-chloroalk-2-enes [78]. For example cyclohexa-1,3-diene and cyclohepta-1,3-diene afforded the corresponding chloroacetates 58a and 58b in good yield and >98% cis selectivity [Eq.(41)]. Cycloocta-1,3-diene gave a 61% yield of acetoxychlorination product (>98% cis), but in this case a 3 1 mixture of 1,4-and 1,2-addition products was formed. A number of substituted cyclic conjugated dienes work well, and, in all cases tried, the reaction proceeds with >97-98% cis selectively [52,78-81]. 

The common preparative method for 7r-allylnickel halides is at the moment the reaction of nickel(O) olefin complexes like bis(cycloocta-1,5-diene) nickel, (IV), with allylic halides (23). The olefin complex, IV, can be prepared easily by reducing nickel(II) salts (like nickel acetyl-acetonate) with aluminum organic compounds in the presence of cycloocta-1,5-diene (5). 7r-Allylnickel halides and substituted 7r-allylnickel halides prepared according to this method are listed in Table I. 

Further studies on the photoisomerization of ci5-cyclohexene and cycloocta-1,3-diene have been reported. Again the work has focused on enantiodiffer-entiation. In this case a series of optically active chiral sensitisers (3) have been used under conditions where solvent and temperature have been varied. Some of the o-disubstituted and tetra substituted amide sensitisers afford mixtures with enantioisomeric excesses of 14%. The influence of pressure and temperature on the asymmetric photochemistry of cyclooctene has been reported. A variety of chiral sensitisers were used. Some of these are shown in (4). Other work has shown that aromatic phosphates, phosphinates and phosphines (e.g. 5-8) can also sensitise the isomerism of cyclooctene. Moderate stationary-state ratios were obtained. 

Table 3. Formation of Substituted 2-(Alk-l-enyl)cyclopropanecarboxylates by [2 + 1] Cycloaddition of 3,3-Disubstituted Cyclopropenes and Alkenes with Electron-Withdrawing Substituents in the Presence of Bis( -cycloocta-l,5-diene)nickel(0)...

Satisfactory yields of cyclocotrimers are obtained with 3,3-dimethylcyclopropene in the presence of alkynes when phosphane-free cobalt(I) catalysts, for example ( j -cycloocta-l,5-diene)( -cyclooctenyl)cobalt(I), are used. The main products are tricyclo[5.1.0.0 - ]oct-2-ene derivatives. Sometimes substituted cycloheptatrienes or the corresponding norcaradienes (bi-... 

In the presence of a bis(ty -cycloocta-l,5-diene)nickel(0)/triaryl phosphite catalyst two molecules of alkyne couple to one cyclopropene moiety yielding substituted norcaradienes and cycloheptatrienes. 

For the dimerization of 2-methyl-, 2,2-dimethyl- and 2,2,3,3-tetramethylmethylenecyclo-propane the bis(cycloocta-l,5-diene)nickel(0) catalyst was modified with dialkyl fumarate, maleic anhydride, or various trialkylphosphanes. For all of the substituted methylenecy-clopropanes but the tetramethyl derivative, dimers of the spiro[2.4]heptane and dispiro[2.1.2.11-octane type were obtained in good yields. 

Only a limited number of vinyl sulfones, e.g. phenyl ( )-2-phenylvinyl sulfone (14), undergo codimerization with MCR Homocyclodimerization of MCP is the most efficient side reaetion. Interestingly, yields and product distributions are solvent dependent. No reaction takes place with catalytic amounts of bis(t -cycloocta-l,5-diene)nickel(0)/triphenylphosphane. In this case the vinyl sulfones are strongly coordinated to the catalyst metal, thus preventing interaction with MCP. When the sulfones bear alkyl-substituted vinyl groups, isomerization to yield allyl sulfones usually proceeds faster than cycloaddition, at least in the case of palladium(O) catalysis. 

The following reactions of norbornene and other nonfunctionalized alkenes with substituted methylenecyclopropanes illustrate these points. (1-Methylethylidene)- and (diphenyl-methylene)cyclopropane (1 R = Me, Ph) give rise to the same type of cycloadducts in the presence of either nickel(O) or palladium(O) catalysts. Even at temperatures as low as 40 "C with bis(> -cycloocta-l,5-diene)nickel(0) as catalyst, 2 may be isolated in 70% yield. The reaction can be extended to vinylbenzene and ethene at temperatures of between 40 and 60 °C, where it may be advantageous to use (cyclododeca-l,3,5-triene)nickel(0) ° as a source of the catalytically active nickel(O) species instead of bis(j7" -cycloocta-l,5-diene)nickel(0). ° This is because ligand dissociation from the former complex is more facile, especially at relatively low temperatures. 

The same is true for alkyl-substituted methylenecyclopropanes, such as butylidenecyclo-propane, which reacts with norbornene to give a modest 34% yield of 4-butylidene-tricyclo[5,2.1.0 ]decane after 3 hours at 95"C in the presence of bis(j7" -cycloocta-l,5-diene)nickel(O) as catalyst. ... 

The reaction of substituted methyienecyciopropanes, such as (1-methylethylidene)- or (diphenylmethylene)cyclopropane, with compound 2 only leads to the formation of [3 -I- 2] cycloadducts. The best combined yield of three isomeric cyclocodimers (93%) is obtained with (1-methylethylidene)cyclopropane in a bis(> -cycloocta-l,5-diene)nickel(0)/tris(2-phenylphenyl) phosphite (1 1) catalyzed reaction at 120°C after 8 hours. ... 

The majority of the presently known A -acyliminium reactions are of this type and have been reviewed extensively. 9 Depending on the substitution patterns of iminium species and ir-nucleophile, either a cycloadduct is obtained as the product, or an acyclic product is isolated, often via the intermediacy of an unstable cycloadduct. When 1,3-dienes are used as nucleophiles they often behave as 4 ir-electron components in a Diels-Alder type reaction (equation 33). Interestingly, cycloocta-1,3-diene, unsuited as a Diels-Alder diene, reacts as an isolated alkene with IV-acyliminium species (129) to give cycloadduct (130) in moderate yield (equation 98). " ... 

Cyclooctadienyl substituents at the methylene groups in c/s-1,4-polybutadiene can be introduced by the radical-induced reaction with cycloocta-1,5-diene. Metathesis degradation of the product with tra 5-oct-4-ene shows that the substitution reaction is accompanied by double-bond shift reactions (Hummel 1990a). 

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