Bicyclo heptenes

CIDNP effects observed for norcarene [147, 178] supported a radical cation, 87 +, which spin and charge are delocalized between the olefinic group and the Walsh orbital of the (more highly substituted) internal cyclopropane bond. The bicyclo-heptene system, 87 +, appears to be more flexible than 86 + either the internal or the lateral cyclopropane bond can align with the alkene p-orbitals. Delocalization of spin and charge into the more highly substituted bond is preferred. 

Arguments similar to those presented above for the hydrovinylation of styrene will dictate the stereochemical course of the reactions involving the other alkenes investigated. Thus, interference of the methylene bridge of a complexed bicyclo-heptene molecule (25) with the substituents on the donor atom and with the complex anion will direct the course of the hydrovinylation reaction to the exo-isomer of (+)-( 5,25,4/ )-2-vinylbicycloheptane (eq. (4)) [3], while the arrangement of the five-membered ring with respect to the coordination plane will result in the conversion of cyclopentadiene into (-)-(f )-3- vinylcyclopentane. 

The antarafacial process here can be excluded since it would produce a highly strained molecule (Fig. 16). In such rearrangements for bicyclo-heptenes and bicyclooctenes there are other examples, however, where the reaction is not so highly stereospecific, or even where retention is favoured over inversion. In such cases one might invoke a nonconcerted... 

The reaction of cyclopentadiene with ethyl acrylate to give the diastereomeric bicyclo-heptenes proceeds more rapidly and with higher en[Pg.205]

The necessity for producing large amounts of synthetic prostaglandins and analogs provided the impetus for a number of improvements in the bicyclo[2.2.1]heptene approach. Especially important was the development of an enantioselective modification for the synthesis of chiral prostanoids without resolution (1975) and the invention of a chiral catalyst for the stereocontrolled conversion of 15-keto prostanoids to either 15(5)- or 15(7 )- alcohols. 

A modification of the bicyclo[2.2.1]heptene route to PC s was developed in which the omega chain was introduced at the end of the synthesis, for the purpose of facilitating the preparation of large numbers of omega-chain-differentiated PG analogs of either the first or second PG family. 

Another interesting fact to be noted is that the bicyclic enamine (87) and its pyrrolidine analogue failed to undergo reduction with 98% formic acid, whereas the pyrrolidine enamine of 2-bicyclo[2.2.1]hepten-5-carboxalde-hyde (94), which exists largely in the transoid form (49), was readily reduced to (95). However, the saturated amine-substituted norbornane can be obtained directly from norbornanone under the more vigorous conditions of the Leuckart reaction (49a). 

The reaction of morpholine with tricyclo[2.2.1.0 ]hcptan-3-one (35) and with 5-bicyclo[2.2.1]hepten-2-one (36) does not proceed in the... 

The above assumes that C protonation is not excluded for steric reasons. Thus N protonation takes place with derivatives of dehydroquinuclidine and the alkaloids neostrychnine and trimethylconkurchine (( ). N protonation was also believed to occur in the case of 2-N-hexamethyleneimino-bicyclo[l,2,2]-2-heptene, which was believed to give the nortricyclene derivative (6) on protonation with perchloric acid. Later work, however, showed the salt to be the results of C protonation (15) and to have structure 7. 

Addition, acetic acid to bicyclo[2.2.1]-hepta-2,5-diene to give nortri-cyclyl acetate, 46, 74 1,2,3-benzothiadiazole 1,1-dioxide to cyclopentadiene, 47, 8 benzyne to tetraphenylcyclopentadie-none, 46,107 Br, F to 1-heptene, 46,10 carbon tetrachloride to olefins, 46, 106... 

The enol ether double bond contained within the ds-fused dioxa-bicyclo[3.2.0]heptene photoadducts can also be oxidized, in a completely diastereoselective fashion, with mCPBA. Treatment of intermediate XXII, derived in one step from a Patemo-Buchi reaction between 3,4-dimethylfuran and benzaldehyde, with mCPBA results in the formation of intermediate XXIII. Once again, consecutive photocycloaddition and oxidation reactions furnish a highly oxygenated system that possesses five contiguous stereocenters, one of which is quaternary. Intermediate XXIII is particularly interesting because its constitution and its relative stereochemical relationships bear close homology to a portion of a natural product known as asteltoxin. 

Phenyl-bicyclo[2.2.1]hepten-(2) liefert unter Angriff des Hydrids von deraro-Seite her das endo-2-Phenyl-bicyclo[2.2.1Yieptanl ... 

Selektiv gelingt die Reduktion einer C=C-Doppelbindung mit Lithiumalanat im 7-Hydroxy-bicyclo[2.2.1]heptadien zum anti-7-Hydroxy-bicyclo[2.2.1]hepten (—100% d.Th.)3 ... 

Die Reduktion von l,2,3,4,7,7-Hexachlor-5-endo-acetoxy-bicyclo[2.2.1]hepten mit Chrom(II)-acetat in Essigsaure fiihrt zum 1,2,3,4,7-syn- (78% d.Th.) und 1,2,3,4,7-anti-(18% d.Th.) Pentachlor-5-endo-acetoxy-bicycIo[2.2. / hepten4 ... 

Steht keine 7-Chlor-Bindung zur Verfiigung, so wird die Briickenkopf-C-Hal-Bindung angegriffen. So erhalt man z. B. aus l,2,3,4-Tetrachlor-7,7-dimethoxy-bicyclo[2.2.1]hep-tan mit Athylendiamin-chrom(II)-perchlorat [32 Aquiv. Chrom(II) pro Mol zu reduzie-rende Substanz ] in waBrigem Dimethylformamid 2,3-Dichlor-7,7-dimethoxy-bicyclo [2.2.I]hepten (63% d.Th. F 54-54,5°) [mit weniger Chrom(II)-Komplex entsteht ein Gemisch aus 1,2,3-Trichlor- und 2,3-Dichlor-Derivat]1. 

Analog erhalt man aus7,7-Dibrom-bicyclo[4.1.0]hepten-(3) 7-Brom-bicyclo[4.1. Oftep-ten-(3) (80-90% d.Th.). 

Die Reduktion von 2-Brom-l-jod-bicyclo[2.2.1]heptan fiihrt zuBicyclo[2.2.1]hepten-(I), das als Diels-Al-der-Addukt mit Furan isoliert wird5. 

With the growing interest for the polynorbomene, photoresist polymer, and cyclic olefin copolymer, the synthesis norbornene or bicyclo[2,2,l]-2-heptene (NBN) has drawn significant attention because it is one of the most important precursor for these materials. Norbornene is produced by the reaction between ethylene and cyclopentadiene (CPD) via the Diels-Alder condensation process at elevated temperature and pressure [1,2]. 

Because aldrin contains the bicyclo-(2.2.1)-heptene ring structure, it reacts typically with phenyl azide to form a phenyldihydrotriazole derivative. This reaction is of importance in that it provides the basis for an analytical method for determining aldrin (discussed more fully in 2). 

Dimalone [bicyclo-(2.2.1)-5-heptene-2,3-dicarboxylic acid dimethyl ester] and Octa-cide 264 [the V-octyl imide of bicyclo-(2.2.1)-5-heptene-2,3-dicarboxylic acid] do produce a red color with an absorption maximum in the same region as that obtained in the analysis of Compound 118. However, because Dimalone is an insect repellent and Octacide 264 is a pyrethrum synergist, neither of these products is likely to be encountered in commercial mixtures of Compound 118. The response to the colorimetric test for Compound 118 of some chemicals commonly used for insect control is listed in Table V. 

Fig. 17. a) Some interesting molecules that undergo 1-3 sigmatropic shifts, b) Clockwise (CW) and counterclockwise (CCW) rotation at the migrating center, c) Mechanisms and parameters for the EHT study of the rearrangements of bicyclo [3.2.0] heptenes with and without inversion of configuration. 

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