Cyclooctadienes electrophilic addition

The electrophilic addition of iodine donors to 1,5-cyclooctadiene (3) gives, analogously to those of BrX, a product distribution which is strongly dependent on the nature of the nucleophile and reaction conditions. 

Thiiranes can be formed directly and stereospecifically from 1,2-disubstituted alkenes by addition of trimethylsilylsulfenyl bromide, formed at -78 C from reaction of bromine with bis(trimethylsilyl) sulfide (Scheme 7).12 A two-step synthesis of thiiranes can be achieved by addition of succinimide-A/-sulfe-nyl chloride or phthalimide-A -sulfenyl chloride to alkenes followed by lithium aluminum hydride cleavage of the adducts (Scheme 8).13 Thiaheterocycles can also be formed by intramolecular electrophilic addition of sulfenyl chlorides to alkenes, e.g. as seen in Schemes 914 and 10.13 Related examples involving sulfur dichloride are shown in Schemes 1116 and 12.17 In the former case addition of sulfur dichloride to 1,5-cyclooctadiene affords a bicyclic dichloro sulfide via regio- and stereo-specific intramolecular addition of an intermediate sulfenyl chloride. Removal of chlorine by lithium aluminum hydride reduction affords 9-thiabicyclo[3.3.1]nonane, which can be further transformed into bicyclo[3.3.0]oct-1,5-ene.16... 

The electrophilic additions of formic and acetic acids to l,5-dimethyl-l,5-cyclooctadiene yielded mainly - 5yu-8-substituted-l,5-dimethylbicyclo[3.2.1]octanes (equation 10) via parallel jr-cyclization and subsequent Wagner-Meerwein (W-M) type rearrangement. Cross TT-cyclization leading to bicyclo[3.3.0]octane derivatives, which were the major adducts in other electrophilic additions to unsubstituted l,5-cyclooctadiene2 22 comprised only a minor route. This different behavior has been interpreted (equation 11) in terms of a significantly larger stability of the tertiary carbocation II than that of the secondary ion in, both ions being the two potential intermediates derived from I by a parallel and a cross jr-cyclization, respectively. 

It is generally assumed that the Lewis acid in 3 decreases the charge on the metal, i.e., increases its electrophilicity. The removal of charge from the nickel allows additional electron donors to coordinate to the nickel atom, and reaction with, for example, 2 moles of carbon monoxide or 1 mole of 1,5-cyclooctadiene (COD) gives the insoluble, catalytically inactive and presumably ionic complexes 7 and 8. In contrast, 7r-allyl-nickel halides (1) add only 1 mole of carbon monoxide while they do not react with COD (52). 

The electrophilic anti- 1,2-addition of the elements of MeSF to C=C has been achieved by a one-pot reaction of Me2S+-SMe BF4- and Et3N.3HF with various types of alkenes267. Markovnikov products arise from unsymmetrically substituted olefins. The reaction of 2,6-norbomadiene proceeds with exclusive exo-attack on one double bond followed by participation of the second double bond to give rise to two isomeric 3,5-disubstituted nortricyclanes267. By contrast, no transannular --participation has been observed with 1,5-cyclooctadiene. The reaction is believed to occur via the corresponding thiiranium species267. 

The cis addition of nitrosyl chloride to cyclic unconjugated polyenes was observed in dichloromethane28. From cyclooctadiene a single diastereomeric dimer 3 (either meso or dl) was produced due to conformational factors associated with the cis configuration. This product underwent transannular electrophilic reaction to give 4. From (Z,Z,Z)-l,5,9-cyclododecatriene the chloro nitroso adduct 5 was obtained as a mixture of the meso and dl forms and was converted to -chloro amine 6 by lithium aluminum hydride/aluminum trichloride reduction 6 was converted to the corresponding aziridine. 13C-NMR spectroscopy was extremely useful in determining the diastereomeric composition of the nitroso dimers. 

Endocyclic cyclooctadienes are transformed into bicyclic products by initiating the reaction with the addition of an electrophile to one double bond. Anti attack of the nucleophilic olefin on the initiating cation results in a defined stereochemistry of the electrophile and bridgehead hydrogen in the bicyclic product. With a non-nucleophilic counterion proton elimination can be observed in the termination step8-9. 

The kinetics of the ADMET reaction is not amenable to study by many traditional means, as these polymerizations are mostly conducted in bulk. The most effective way to measure the kinetics of the polymerization is to monitor the volume of evolved ethylene. This technique has been used to probe the difference in activity between [Mo] 2 and [Ru]l for ADMET polymerization of 1,9-decadiene [37]. At 26 °C in bulk monomer, [Mo] 2 promotes ADMET polymerization of 1,9-decadiene at a rate approximately 24 times that of [Ru]l. Additionally, [Mo] 2 polymerizes 1,5-hexadiene 1.7 times faster than 1,9-decadiene, while [Ru]l only cyclodimerizes 1,5-hexadiene to 1,5-cyclooctadiene. Monomers with coordinating functionality, specifically ethers and sulfides, were also investigated. Predictably, these monomers did not undergo polymerization as rapidly as hydrocarbon monomers however, this difference was dramatically more pronounced with [Ru]l than with [Mo]2. In fact, the dialkenyl sulfide monomers that were studied completely shut down the polymerization with [Ru]l, whereas the catalytic activity of [Mo]2 was only slightly lowered. This reduction in polymerization rate is most likely due to coordination of the heteroatom to the vacant coordination site of [Ru] 1, following phosphine dissociation. This reversible coordination of heteroatoms to the ruthenium complex likely occurs both intramolecularly and intermolecularly. Conversely, the steric bulk of the ligands in [Mo] 2 makes it less likely to intramolecularly form a coordinate complex, despite molybdenum being far more electrophilic than ruthenium. 

The addition of f-BuLi in diethyl ether at -78 °C to 3-methylene-l,4-cyclooctadiene was used to generate a cyclooc-tadienyl anion that undergoes disrotatory ring closure to deliver a d5-bicyclo[3.3.0]octenyllithium that may be trapped with any of a variety of electrophiles to give 4-substituted cis-bicyclo[3.3.0]octenes in good yield (eq 44). ... 

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