1,5-Cyclooctadiene carbonylation

The oligomerization and cooligomerization of conjugated dienes are representative reactions that proceed via transition-metal Jt-allyl intermediates. When (CsMesjRuCljt/ -butadiene) in dichloromethane was treated with an acetone solution of an equimolar amount of silver trifluoromethanesulfonate (AgOTf) in the presence of excess butadiene at ambient temperature, after which the mixture was allowed to react with carbon monoxide (1 atm), a cationic 1,5-cyclooctadiene carbonyl complex, [(C5Me5)Ru(CO)( -l,5-C8Hi2)]OTf, was isolated in 95% yield (Eq. 

A novel route to azelaic acid is based on butadiene. Butadiene is dimerized to 1,5-cyclooctadiene, which is carbonylated to the monoester in the presence of an alcohol. Hydrolysis of this ester foUowed by a caustic cleavage step produces azelaic acid in both high yield and purity (56). 

A particularly useful phosphine ligand for the cobalt carbonyl catalyst is a bicyclic tertiary phosphine available from 1,5-cyclooctadiene, phosphine, and an a-olefin ... 

Nickel carbonyl is an extremely toxic substance, but a number of other nickel reagents with generally similar reactivity can be used in its place. The Ni(0) complex of 1,5-cyclooctadiene, Ni(COD)2, can effect coupling of allylic, alkenyl, and aryl halides. 

Section B of the Scheme 9.1 shows several procedures for the synthesis of ketones. Entry 6 is the synthesis of a symmetrical ketone by carbonylation. Entry 7 illustrates the synthesis of an unsymmetrical ketone by the thexylborane method and also demonstrates the use of a functionalized olefin. Entries 8 to 10 illustrate synthesis of ketones by the cyanide-TFAA method. Entry 11 shows the synthesis of a bicyclic ketone involving intramolecular hydroboration of 1,5-cyclooctadiene. Entry 12 is another ring closure, generating a potential steroid precursor. 

This reaction sequence of conjugate reduction followed by aldol reaction is known as the reductive aldol reaction. In certain instances, reductive elimination from the M-TM-enolate species may occur to furnish M-enolate, which itself may participate in the aldol reaction (Scheme 3). This detour may be described as the background path or stepwise path in one-pot. Indeed, it has been reported that certain cationic Rh complexes such as [Rh(COD)(DPPB)] (COD = 1,5-cyclooctadiene, DPPB = diphenylphosphinobutane) catalyze the aldol reactions of silyl enol ethers and carbonyl compounds by serving as Lewis acids [5-8]. 

Bis(0-salieylidenaminopropylaziridine)iron(III) perchlorate, 3853 Bis(tetramethyldiphosphane disulfide)cadmium perchlorate, 3102 Carbonyl-bis(triphenylphosphine)iridium-silver diperchlorate, 3898 5-/ -Chlorophcnyl-2.2-dimcthy 1-3-hcxanonc. 3664 Copper(II) perchlorate, Polyfimctional amines, 4057 Copper(II) perchlorate, /V-(2-Pyridyl)acylacctamidcs. 4057 2(5-Cyanotetrazole)pentaamminecobalt(III) perchlorate, 0974 1,5-Cyclooctadiene-bis(4-chloropyridine /V-oxidc)rhodium(I) perchlorate, 3761... 

A wide range of carbon, nitrogen, and oxygen nucleophiles react with allylic esters in the presence of iridium catalysts to form branched allylic substitution products. The bulk of the recent literature on iridium-catalyzed allylic substitution has focused on catalysts derived from [Ir(COD)Cl]2 and phosphoramidite ligands. These complexes catalyze the formation of enantiomerically enriched allylic amines, allylic ethers, and (3-branched y-8 unsaturated carbonyl compounds. The latest generation and most commonly used of these catalysts (Scheme 1) consists of a cyclometalated iridium-phosphoramidite core chelated by 1,5-cyclooctadiene. A fifth coordination site is occupied in catalyst precursors by an additional -phosphoramidite or ethylene. The phosphoramidite that is used to generate the metalacyclic core typically contains one BlNOLate and one bis-arylethylamino group on phosphorus. 

Ikegami has devised an interesting approach based upon 1,3-cyclooctadiene monoepoxide as starting material (Scheme LX) Transannular cyclization, Sharpless epoxidation, and silylation leads to 638 which is opened with reasonable regioselec-tivity upon reaction with l,3-bis(methylthio)allyllithium. Once aldehyde 639 had been accessed, -amyllithium addition was found to be stereoselective, perhaps because of the location of the te -butyldimethylsilyloxy group. Nevertheless, 640 is ultimately produced in low overall yield. This situation is rectified in part by the initial formation of 641 and eventual decarboxylative elimination of 642 to arrive at 643. An additional improvement has appeared in the form of a 1,2-carbonyl transposition sequence which successfully transforms 641 into 644... 

These compounds have been obtained indirectly by reactions of silylated acetylenes with metal carbonyls or olefin complexes. Thus, trimethylsilylphenylacetylene reacts with rj5-cyclopentadienylcobalt dicarbonyl, cobaltocene, or rjs-cyclopentadienyl-(l,3-cyclooctadiene) cobalt, in refluxing xylene, to give a mixture of cis- and trans-bis-(trimethylsilyl)cyclobutadiene complexes (R = Me, R = Ph) 68, 127, 137) ... 

Linear and cyclic diolefins form a variety of clusters with trirutheniumdodeca-carbonyl or the tetraruthenium carbonyl hydrides. These belong to the compound types H2Ru3(CO)9L [56] or HRu3(C0)gl/ [55]. Type [56] complexes are obtained from cyclopentadienes (27 7), cyclooctadienes (74), or bicyclooctadiene (146). 

In the carbonylation of unconjugated dienes the nature of the products is influenced by reaction conditions. With Pd halides in ethanol at 100°C and 97 atm CO, 1,5-cyclooctadiene is successively carbonylated to the unsaturated monoester and then to the saturated diester (II). With (Ph3P)2PdCl2 in ethanol-HCl and 300-700 atm CO, the monoester is produced selectively at 60°C and the diester at 100°C (8). Finally, with (Bu3P)2PdI2 in THF at 150°C and 1000 atm CO, 1,5-cyclooctadiene undergoes transannular addition of CO to give a cyclic ketone in 40-45% yield (14, 15). The mechanism proposed involves a a-7r-cyclooctenyl... 

Transfer hydrogenation of dienes to monoenes 1,5-Cyclooctadiene is selectively reduced to cyclooctene by transfer hydrogenation with isopropanol catalyzed by this metal carbonyl cluster. The first step is isomerization to conjugated diene isomers. 1,5-Hexadiene is reduced under these conditions to frms-3-hexene (19%), os-2-hexene (21%), trans-2-, and cw-3-hexene (56%). Ru3(CO)i2, Os3(CO)12, and Ir4(CO)i2 catalyze isomerization of 1,5-cyclooctadiene, but are less active than Rh6(CO)i6 for transfer hydrogenation. 

Reaction at a higher temperature for a longer period leads to formation of the ruthenium carbonyl complex [IR(KBr) 1964 cnv ], This undesired reaction is suppressed under the present conditions. Use of commercial [RuCl2(1,5-cyclooctadiene)]n or readily available RuCl2[Sb(CaHs)3]33 gives similar results on heating in DMF at 160°C for 20 min or in o-dichlorobenzene at 160°C for 10 min. N.N-Dimethylacetamide can be used in place of DMF. 

There are a few reports in the literature in which the carbonyl group has been formally replaced by another unsaturated function. Thio-benzophenone (268) undergoes photochemical 1,2-cycloaddition to a-phellandrene (269) to give the thietane (270), together with the sulfur heterocycles (271 and 272) formed by 1,4-cycloaddition.298 Isoprene, cyclopentadiene, and 1,4-diphenylbutadiene also undergo 1,4-cycloaddition with thiobenzophenone, but 1,3-cyclooctadiene... 

The hydroesterification of dienes gave both the unsaturated monoesters and saturated diesters.524 In some cases, y-ketoesters were obtained and carbonylation of 1,5-cyclooctadiene in absence of alcohol gave a ketone.525 [PdI2(PBu3)2] was used as catalyst. If the catalyst contained a halide anion, butadiene underwent normal hydroesterification. When halide-free catalysts were used, the reaction took a different course. Dimerization of the diene occurred to give the ester of 3,8-nonadienoic acid as the major product (equation 128).526-528... 

The mono(diphosphine) complexes, [Rh(dppp)]BF4 and RhCl-(dppp), are less effective than [Rh(dppp)2] + but are still more active than RhCl(PPh3)3. The mono(diphosphine) catalysts also decompose slowly under the reaction conditions, which renders them less useful than the bis(diphosphine) catalysts. The slower rate of decarbonyla-tion observed with the mono(diphosphine) catalysts compared with the bis(diphosphine) catalysts presumably is due to the lower basicity of the former which retards the rate of oxidative addition (vide infra). Consistent with this is the observation that [Rh(COD)(dppp)]BF4 (COD = 1,5-cyclooctadiene) shows a higher rate for catalytic de-carbonylation of benzaldehyde than does [Rh(dppp)]BF4 (22). An additional observation is that the type of anion, Cl or BF4 , has no apparent effect on decarbonylation rates for the bis(diphosphine) catalysts however, for the mono(diphosphine) complexes the chloride salts show slightly lower rates than their tetrafluoroborate analogues. 

---