Bicyclo 2.2.2 octene derivative

The corresponding bicyclo[2.2.2]octene derivatives provided an equilibrium mixture (8 1) with only minor amounts of the retro-Claisen product36. The Diels - Alder adduct from diphenylful-vene and (Z)-hex-3-en-2,5-dione rearranged completely to the corresponding dihydropyran at 45°C in ethanol37. 

The results for bicyclo[2.2.2]octene derive from the fast reversible formation of mercurium ions, which, if captured rapidly by the solvent, give products of anti addition, but, if attacked only slowly, give products derived from carbonium ions, i.e., rearranged products or syn adducts. 

An enzymatic approach has been advocated for the single-step preparation of small quantities of enantiomerically enriched 2-oxynorbomanes and 2-oxybicyclo[3,2,l]-octanes. Thus, for example, horse fiver alcohol dehydrogenase-catalysed oxido-reduction of ( )-2-norbornanone results in the production of (—)-(lR,4S)-2-nor-bornanone and (-f)-(lS,21, 4R)-endo-2-norbomanol of up to 46 and 66% optical purity respectively. The space-conjugated olefinic double bonds in various nor-bornene and bicyclo[2,2,2]octene derivatives are rapidly reduced by lithium in liquid ammonia benzonorbomadiene, for example, is reduced to benzonorbomane. ... 

The number of reaction types that we have covered to this point is extensive enough to allow the construction of relatively complicated products from simple, readily available starting materials. Thus, recognizing that the bicyclo[2.2.2]octene derivative shown is accessible by a Diels-Alder reaction leads us back to cyclohexanol as the source of six of its carbons. 

Luciduline is one of the simpler Lycopodium alkaloids. In an elegant synthesis of this molecule, Scott and Evans constructed the desired tricyclic skeleton from the key decalin ketoamine (D) by an intramolecular Mannich reaction, C-11 being derived from formaldehyde. The c/i-decalin-2,6-dlonesuitable for preparation of (D) was obtained by the oxy-Cope rearrangement of a bicyclo[2-2-2]octene derivative (A) which allowed controlled introduction of the desired sites of asymmetry. 

Cationic cycloadditions. Ionization of p-benzoquinone monoacetals is induced by MejSiOTf in highly polar media (LiClO /EtOAc) and the carbocations are captured in situ by alkenes to give bicyclo[3.2.1]octene derivatives. A synthesis of 2-(l -phenylethoxy)-8-oxabicyclo[3.2.1]oct-6-en-3-one in good enantiomeric purity from furan and a mixed acetal of 2-(triethylsiloxy)acrolein (prepared from pyruvaldehyde dimethylacetal in three steps) is promoted by MejSiOTf. 

Cyclopropylideneacetates also undergo [4-1-2] cycloadditions to yield spiro[2.5]octene derivatives. The relative Diels-Alder reactivities of 2-heteroatom-substituted 2-cyclo-propylideneacetates, as determined by competition experiments with furan to give 7-oxa-bicyclo[2.2.1]heptanes 18, have been studied. The 2-chloro and 2-bromo derivatives were equally reactive and underwent cycloaddition ca. 16 times faster than methyl acrylate, which in turn is far more reactive than methyl 2-chloro-3,3-dimethylacrylate. Selected examples of [4-1-2] cycloadditions are given in Table 4, for further examples see refs 10, 22, 44 and 45. 

The addition of dihalocarbenes to double bonds is straightforward, but the use of substrates with strained double bonds has been observed to lead to rearranged products. For example, norbornene gives the bicyclo[3.2.1]octene derivative (Scheme 5.53). 

Hatanaka and coworkers [28] developed an intramolecular cycloaddition route of 4-alkenylfulvene 115 to give the bicyclo[3.3.0]octene derivative 118 (Scheme 7.27). Treatment of the ynone 113 with 2-ethoxyallyhdenetriphenylphosphorane 114 in THF afforded a mixture of Z-fulvene and -fulvene isomers 115. The fulvenes are formed via initial conjugate addition of the phosphorane to the... 

COT is prepared by the polymerization of ethyne at moderate temperature and pressure in the presence of nickel salts. The molecule is non-planar and behaves as a typical cyclic olefin, having no aromatic properties. It may be catalytically hydrogenated to cyclo-octene, but with Zn and dil. sulphuric acid gives 1,3,6-cyclooclairiene. It reacts with maleic anhydride to give an adduct, m.p. 166 C, derived from the isomeric structure bicyclo-4,2,0-octa-2,4,7-triene(I) ... 

Askani, R Ober einige Bicyclo[4.2.0]octen- und Bicyclo[3.2.0]hepten-Derivate. Chem. Ber. 98, 2322 (1965). 

An important field of application of the 1,3-elimination method concerns those compounds where oxiranes can be obtained with configurations opposite to those of the oxiranes resulting from the peracid method. Examples are the stereoselective epoxidation of a methylenecyclohexane derivative with NBA/KOH, the epoxida-tion of 3-alkylcyclopentene and 3,4-dialkylcyclopentene with NBS/KOH, and the /3-epoxidation of bicyclo[3.3.0]octene and bicyclo[4.3.0]nonene. The different stereoselectivities can be interpreted on the basis of the mechanisms of the... 

Corey-Winter olefin synthesis (1, 1233-1234). Chong and Wiseman1 were able to demonstrate the transient existence of bicyclo[3.2.1]octene-l (2, a bridgehead alkene which violates Bredt s rule) by application of the Corey-Winter olefin synthesis. Thus treatment of the thionocarbonate (1) with triethyl phosphite at reflux (165°) for 24 hr. in the presence of 1,3-diphenylisobenzofurane (1, 342-343 2, 178-179) leads to the formation of two Diels-Alder adducts (3) and (4) derived from (2). 

Potassium fluoride in a two-phase system was also efficient when 18-crown-6 was present as a phase-transfer catalyst. The desilylation by fluoride produced a 7-0x0 enolate which could be reacted with various electrophiles. Appropriately substituted bicyclo[3.1.0]hexane derivatives 42 and 44 have been used to study this reaction.a,/l-Unsaturated carbonyl compounds gave rise to the formation of Michael adducts, while treatment with triphenylvinylphos-phonium salts gave bicyclo[3.3.0]octenes 46 as the result of a subsequent intramolecular Wittig reaction. 

Wahrend unsubstituierte Bicyclo[2.2.2]octene mit Metall/fl. Ammoniak/Alkohol schwer reduzierbar sind, werden die am Briickenkopf-Atom durch Alkoxy- oder Ami-no-Gruppen substituierten Derivate leicht angegriffen z.B.2 ... 

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