Quadricyclane derivative, reaction

Like the cyclization of the parent system, the photocyclization of hetero analogues of norbornadiene was reported many years ago. Recent interest in this area will serve to illustrate the potential of the conversions. Thus the irradiation of the oxanorbomadiene system 259 brings about conversion to the oxepine 260138. The formation of 260 presumably arises by quadricyclane 261 formation, followed by secondary photolytic ring-opening. Other research has shown that irradiation of the oxanorbomadiene 262 follows the same reaction mode and it undergoes (2 + 2)-cycloaddition to the quadricyclane derivative 263. Apparently, in this instance, cycloreversion affords the ylide 264 that can be trapped by suitable addends, giving the adducts illustrated in Scheme 3139. 

The quinones (373) are photochemically reactive and are converted into the quadricyclane derivatives (374) by use of light of wavelength > 410 nm. The yields are generally high (> 63 X) and the quantum efficiency is about 0.21. The reaction appears to be unaffected by the methoxy and methyl substitution. - ... 

The Ag+ ion-catalyzed reaction of a quadricyclane derivative also appears to proceed through initial C-C bond insertion [Eq. (6.110)] ... 

One typical example is given by G. Kaupp with the [2+2] cycloaddition of diphenyl-acetylene to 1,4-dioxene leading to a bicyclic cyclobutene in good yield (cf. iv of this chapter). Another example is presented by T. Miyashi starting from naphthoquinonor-bomadiene. In an intramolecular reaction a quadricyclane derivative is quantitatively formed upon irradiation at X > 400 nm. It is assumed that this process involves the diketo-norbomadiene in its triplet state. Although the spin multiplicity of intermediates have not... 

Toda and co-workers have published a full paper on the preparation of the benzo-l,2 4,5-dicyclobutadiene (141), and have described some more of its reactions. Addition of diphenylcyclopropenone in refluxing xylene gave the novel quadricyclane derivative (142), which rearranged on further heating. Reaction of (141) with tetra-cyanoethylene resulted in an olefin metathesis reaction with one of the cyclobutadiene double bonds to give (143), but with dimethyl maleate, ° addition took place... 

When additional substituents are introduced in the 2- and/or 4-position, the thermal rearrangement gives products in which the substituents that were originally located in the 1- and 5-position of the quadricyclane are then located at C4 and C5 of the oxepin 7.30,123 In order to trap intermediates of this rearrangement reaction by intramolecular cycloaddition vinyl and acetylene groups were linked with different spacer groups to C2 of quadricyclane.123 In this manner two different intramolecular cycloadducts were isolated in addition to oxepin derivatives.123... 

The irradiation of the norbornadiene derivatives (148) yields the quadricyclanes (149). These quadricyclanes can be reconverted to the starting material by treatment with silver ion. The norbornadienes (150) photochemically ring close to the quadricyclanes (151). Both direct and sensitized irradiation were used but the direct irradiation afforded a mixture of products. The reactions were much cleaner using benzophenone as the sensitizer. Irradiation of the norbornadiene derivative (152) affords the quadricyclane (153). Paquette and Racherla - have synthesized the norbornadiene (154) in which it is claimed that homoconjugation is high. This is borne out on acetophenone-sensitized irradiation in pentane when it is converted to the quadricyclane (155). Prinzbach and his coworkers have reported on the photochemical (2+2)-cycloadditive behaviour of adducts of the type represented by (156). The acetone-sensitized irradiation of this compound brings about (2 + 2)-cycloaddition to afford a 2 1 mixture of the adducts (157) and (158). Direct irradiation, however, follows a different path to yield a mixture of the (2+2)-adduct (157) as... 

Quadricyclane (2) and its derivatives are quite reactive as bishomodienes, reacting with a number of electron-deficient dienophiles to form tricyclo[4.2.1.0 ]non-7-ene derivatives 8. The reactions are regio- and stereoselective. The configuration of the dienophile is retained in the product, the four-membered ring is exo, and the substituents of (Z)-disubstituted dienophiles are endo or exo depending on the substituents. ... 

By reaction with sodium dithionite, the diphenyl- and triphenylcyclopropenylium ions 5 (R = H, Ph) were transformed into the dicyclopropenyl sulfone derivatives 6, which upon photolysis were cleanly converted into tetraphenyl- or hexaphenylbenzene (8, R = H, Ph), presumably through formation of the quadricyclane-type derivative 7. ... 

No detailed mechanistic interpretation of the catalysis of the conversion of quadricyclane to norbornadiene by these triphenylcyclopro-penylnickel derivatives is warranted at the present time. However, these reactions appear to be quite similar to isomerizations of quadricyclane to norbornadiene catalyzed by other nickel complexes (14). 

PET is the key feature of many other photo-oxidations involving aromatic substrates. It has been shown, for example, that pyrene and anthracene which are covalently attached to silica, gold or indium-doped tin oxide (ITO), undergo a photo-oxidation forming dihydroxy/dione derivatives. The reaction involves 02, formed by ET between excited pyrene, or anthracene, and O2, and it is suggested that the implications of such a photodegradation need to be considered when polycyclic aromatic hydrocarbons (PAHs) are used as spectroscopic probes in surface adlayers. The redox photosensitized amination of 1,2-benzo-1,3-cycloalkadienes, arylcyclopropanes, and quadricyclane with ammonia and primary amines, using 1,2,4-triphenylbenzene (1,2,4-TPB) or 2,2 -methylenedioxy-1,1 -binaphthalene in the presence of m- or p-dicyano-benzene (DCB), has been described (Scheme 51). The process involves the formation of the radical cation of 1,2,4-TPB, for example, by PET to the DCB, followed by hole transfer from the radical cation to the substrate, the latter... 

In contrast to bis-SiMey-norbornene derivatives, disubstituted tricyclononenes turned out to be active monomers in AP [238, 240]. In tricyclononene molecule both MesSi-groups are moved by an additional one C-C bond away from the double bond and therefore from the reaction catalytic center. Synthesis of bis-MesSi-substituted tricyclononene was carried out from quadricyclane and fran5-l,2-bis(trichlorosilyl)ethylene. This route of synthesis provided formation of norbomene-type monomers with 100% exo-configuration of cyclobutane fragment that reduced steric hindrances in AP. That is why this monomer was active in AP catalyzed with common Ni- and Pd-catalyst systems. As a result, the formation of highly molecular weight polymer (Af up to 500,000 was observed [196]. 

The poly-isoprene derivative 106 readily undergoes photochemical isomerization to quadricyclane 107 in the presence of (PPh3)2CuBr in benzene solution. The reaction in the solid state is thermally reversible... 

Styrene derivatives are commonly used addends in the photocycloaddition studies of 1,4-quinones. With Z- and -anethole, 1,4-benzoquinone (BQ), 1,4-naphthoquinone (NQ), and 9,10-anthraquinone in acetonitrile solvent yield spiro-oxetanes in which the trans-isomer (e.g., 4 from naphthoquinone) predominates. The process has been studied in detail by CIDNP techniques from which it is deduced that product formation proceeds from triplet radical ion pairs to the triplet biradical, and that there is no significant contribution from direct conversion of exciplex intermediates into the biradicals. Spiro-oxetane formation between simple alkenes and BQ generally has low regioselectivity but this is markedly improved with alkylidene cyclohexanes (Figure 87.3) such that the major isomer can be used as a new access to useful synthetic building blocks. For the BQ/homobenzvalene 5 system, however, where the difference in stability between the intermediate biradicals can be expected to be considerably less, the selectivity ratio for the spiro-oxetanes 6 and 7 is reduced to 3 1, respectively, and the addition to NQ yields only the cyclobutane derivative 8. Quadricyclane and norbornadiene undergo the same photocycloaddition reaction to BQ, affording the oxolane 9 and the spiro-oxetane 10. Evidence from CIDNP... 

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