Cyclooctadienes transannular reactions

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. 

In route A, one electron is removed fiom cme double bond to generate a cation radical, and subsequent transannular reaction of the cation radical with the other double bond forms a new carbon-carbon tend. On the other hand, in route B, allylic substitution or oxidative addition at one double bond takes place without intramolecular interaction between the double bonds. As exemplified by the anodic oxidation of 4-vinylcyclohexene (11) in methanol (equation 16), such dienes as 4-vinylcyclohexene, limonene and 1,5-cyclooctadiene yield only products via route B. 

Cyclooctadiene undergoes a transannular reaction to form a bicyclo[5.1.0]octane system 1. The initiating electrophile and terminating nucleophile are trans-located in the product19. 

The copolymer is not strictly alternating, since MA seems only to be incorporated in the intermolecular step the intramolecular step being a transannular reaction of the cyclooctadiene. On the basis of composition, IR and NMR studies, and failure of the polymer to take up bromine, a... 

Nevertheless, a different selectivity has really been observed83 in bromofluorination reactions of 1,5-cycloalkadienes with NBS/Et3N-3HF or Olah s reagent. The reaction of 1,5-cyclooctadiene (3) with the former reagent yields mainly the 1,2-addition product 52, but when the reaction is carried out with Olah s reagent only compounds 53 and 54, arising from the usual transannular jr-cyclization, are formed (equation 53). 

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... 

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... 

Ishii and coworkers developed a Mn(OAc)2-catalyzed hydrophosphonation of alkenes 40 (Fig. 47) [271]. The active Mn(III) catalyst is generated by reaction of Mn(OAc)2 with oxygen. Hydrogen abstraction from diethyl phosphite 169 forms a phosphonyl radical, which adds to 40. The resulting alkyl radical is reduced by 169 to continue the chain reaction. Alkylphosphonates 170 were isolated in 51-84% yield. With (3-pinene a cyclobutylcarbinyl radical ring opening was observed in 32% yield, while 1,5-cyclooctadiene underwent a tandem radical addition/ transannular 5-exo cyclization (cf. Fig. 38). 

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. 

Transannular hydride shifts, first detected by Cope and coworkers in solvolyses of cyclooctene oxide, have subsequently been found in a number of related systems, e.g. cyclooctadiene monoepoxides, CA o-bicyclo[3.3.1 ]non-2-ene epoxide and l-oxaspiro[2.6]nonane. In general these reactions do not involve skeletal rearrangements, and they will not be discussed in detail. 

Transannular carbocyclization in the reaction of cis,cis-l,5-cyclooctadiene yields a mixture of three diastereomers of 2,6-diacetoxy-cw-bicyclo[3.3.0]octane, a useful precursor of cis-bicyclo[3.3.0]octane-2,6-dione (eq 1). ... 

No product derived from the transannular hydrogen abstraction is observed in the addition of bromotrichloromethane, because bromine atom abstraction is sufficiently rapid to prevent effective competition by the hydrogen-abstraction process. Another example of transannular cyclization of unsaturated radicals is found in the reaction of 1,4-cyclooctadiene with acetaldehyde in the presence of benzoyl peroxide, which gives a cyclized ketone by a process involving an intramolecular addi-... 

The synthesis of ( )-anatoxin (46) was elegantly achieved starting from 1,5-cyclooctadiene (47) key transformation is a ring-opening/transannular ring-closure domino reaction of the P-lactam epoxide 48 with methyl lithium giving rise to intermediate 49, from which the target molecule 46 is reached in few conventional steps [29]. 

Winkler and Sridar investigated the transannular radical reaction cascade of 1,5-cyclooctadienes (i.e., 103 and 110) for synthesis of linear triquinanes (Schemes 20.29 and 20.30). The substituents were found to exert subtle... 

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