Bicyclo norbomadienes

As discussed in connection with the facial selectivities of 7-methylidenenorbom-ane 46 and bicyclo[2.2.2]octene 48, the components of the molecules, i.e., n functionality and two interacting o orbitals at the two P positions, are the same, but the connectivity of these fragments, i.e., the topology of the n systems, is different (A and B, Fig. 9). A similar situation was found in the case of spiro[cyclopentane-l,9 -fluorene] 68 [96, 97] and 11-isopropylidenedibenzo-norbomadienes 71 (see 3.4.1 and 3.4.2) [123]. In these systems, the n faces of the olefins are subject to unsymmetrization due to the difference of the interacting orbitals at the P positions. In principle, consistent facial selectivities were observed in these systems. 

The increase in ring size from the norbomadiene-type to bicyclo[2.2.2]octadiene systems appears not to affect the overall reaction outcome. Again the interaction involves... 

These results have been interpreted in terms of trans addition of mercuric ion and nucleophile where the attack of the mercuric ion takes place from the more hindered side of the diene molecule. A transition state 197, involving an endo attack of mercuric ion with some stabilization by coordination to the 8,9-ethylenic bond to the mercury atom, has been proposed to support the suggested mechanism. Analogously, and in sharp contrast to the results obtained167 in the mercuration of norbomadiene which reacts with mercury salts via the usual scheme of exo-syn addition, the principal pathway in the mercuration of bicyclo[2.2.2]octa-2,5-diene is the formation of endo-syn products (equation 165). 

Heterosubstitution at nonactivated positions is also possible by using highly reactive metalating agents such as pentylsodium. When used in the presence of tm-BuOK, it readily and selectively forms vinylsodium derivatives that can subsequently be converted to organosilicium compounds.243 Norbomadiene and bicyclo-[3.2.0]hepta-2,6-diene are also readily silylated via the corresponding sodium compounds formed in the reaction with BuLi-rm-BuONa.244 Similar transforma-tions of strained polycyclic cyclopropanes were also achieved [Eq. (10.45) ] ... 

Strained alkenes such as norbomene, norbomadiene and bicyclo[2.2.2]octenes readily insert into ir-allyl complexes with the less substituted allyl terminus linked to the alkene (equation 81).233-261 This reaction has been utilized to prepare interesting prostaglandin analogs.233 234... 

Bomane Group (BicycloQ2.2.IQ heptane Type). Name the bomane-type bicyclic terpene hydrocarbons (bicycleheptane type) as norbomanes, norbomenes, and norbomadienes and base these names on systematic bicyclo numbering and rules (Formula 73, Chart 9). For those derivatives which have a carbon skeleton identical to bomane, use the bomane, bomene, and bornadiene names, and base these names on the recommended fixed numbering of the bomane carbon skeleton (Formula 75, Chart 8). See Chart 14. 

Norbomadiene 1- and 2-Cyclopropyl-vinyl cyanide 1- and 2-Cyclobutyl-fluoroethylene Silylcyclopentadiene Bicyclo[2,2,l]heptane (norbornane)... 

The telluretane derivative 3,5-dibromo-8-telluratricyclo[2.2.1.1]octane 8,8-dibromide was prepared from tellurium tetrabromide and bicyclo[2.2.1]-2,5-heptadiene (norbomadiene)4. 

Roth, Schilling and coworkers [47-54] have investigated the nuclear spin polarization behavior of cation-radicals of numerous strained hydrocarbon systems produced by PET to strong electron acceptors such as chloranil, anthraquinone and cyanoaromaties. These systems include cyclopentadiene dimers, methyl-enebicyclo[2.2.0]hexenes [48], bicyclo[1.1.0]butanes [49], hexamethyl (Dewar benzene) [50], norbomadiene [53], quadricyclene [53], and 1,2-diphenylcyclopropanes [54]. 

Alternate Name (bicyclo[2.2.1]hepta-2,5-diene)(chiraphos)-rhodium perchlorate (norbomadiene)(chiraphos)rhodium perchlorate. 

Alkene Hydroarylation. The enantioselective addition of aryl iodides to norbomene has been reported using a palladium(II) complex of (5, iS )-CHIRAPHOS. The reaction of norbomadiene with 4-methoxyiodobenzene proceeded with 30% ee (eq 5). Enantioselectivities were dependent upon phosphine structure (see (+)-trans-(2S,3S)-Bis(diphenylphosphino)bicyclo[2.2.1 ]hept-5-ene). 

Many studies used radiation chemistry to produce the radical and radical cations and anions of various dienes in order to measure their properties. Extensive work was devoted to the radical cation of norbomadiene in order to solve the question whether it is identical with the cation radical of quadricyclane . Desrosiers and Trifunac produced radical cations of 1,4-cyclohexadiene by pulse radiolysis in several solvents and measured by time-resolved fluorescence-detected magnetic resonance the ESR spectra of the cation radical. The cation radical of 1,4-cyclohexadiene was produced by charge transfer from saturated hydrocarbon cations formed by radiolysis of the solvent. In a similar system, the radical cations of 1,3- and 1,4-cyclohexadiene were studied in a zeolite matrix and their isomerization reactions were studied. Dienyl radicals similar to many other kinds of radicals were formed by radiolysis inside an admantane matrix. Korth and coworkers used this method to create cyclooctatrienyl radicals by radiolysis of bicyclo[5.1.0]octa-2,5-diene in admantane-Di6 matrix, or of bromocyclooctatriene in the same matrix. Williams and coworkers irradiated 1,5-hexadiene in CFCI3 matrix to obtain the radical cation which was found to undergo cyclization to the cyclohexene radical cation through the intermediate cyclohexane-1,4-diyl radical cation. 

As shown in Table 6 and Figure 1, the oxidation potentials of 2-substituted norbomadienes (1), 2-substituted bicyclo[2.2.2]octa-2,5-dienes (2) and 4-substituted [2.2]paracyclophanes (3) clearly indicate that the transannular interaction between two double bonds contributes already at the stage of the first electron transfer. Namely, in compounds 1-3, the electron is transferred from the unsaturated bond which is not substituted by the electron-withdrawing group, Figure 1 shows the... 

DMF dmso DMSO dpae dpam dppb dppe dppm dppp ET Hdbpz Hdcmpz Hdfmpz Hdmepz Hdmpz Hdppz Hmpz Hpz Hpz Htmpz IR nbd NMR phen /V./V-Dimethylformamide Dimethyl sulfoxide (ligand) Dimethyl sulfoxide (solvent) 1.2- Bis(diphenylarsino)ethane Bis(diphenylarsino)methane 1.4- Bis(diphenylphosphino)butane 1.2- Bis(diphenylphosphino)ethane Bis(diphenylphosphino)methane 1.3- Bis(diphenylphosphino)propane Electron transfer 3.5- Di-ferf-butylpyrazole 3.5- Dicarbomethoxypyrazole 3.5- Bis(trifluoromethyl)pyrazole 3(5),4-Dimethyl-5(3)-ethylpyrazole 3.5- Dimethylpyrazole 3.5- Diphenylpyrazole 3(5)-Methylpyrazole Pyrazole A general pyrazole 3.4.5- Trimethylpyrazole Infrared spectroscopy Norbomadiene (bicyclo-[2.2.1. ]-heptadiene) Nuclear magnetic resonance 1,10-Phenanthroline... 

Equation 7 is related to a Diels-AIder type reaction and led us to examine the reaction of metal dithienes with reactive olefins. With norbomadiene (bicyclo[2.2.1]hepta-2,5-diene) in homogeneous solution (CH2CI2 is a convenient solvent), the Diels-Alder adduct 26 is formed in high yield with the oligomeric nickel(II)-stilbenedithiolate (25) (i6, 17) ... 

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