Bicyclo -hepta-2,5-diene

A direct entry to the quadricyclene series has been gained through photoisomerization of bicyclo [2.2.1 ]heptadienes. Bicyclo [2.2.1 ]hepta-dien-2,3-dicarboxylic acid (Formula 194), undergoes light-induced valence tautomerization to Formula 195 (75). The parent quadricyclene 196 has been prepared by direct irradiation of bicyclo [2.2. l]heptadiene... 

Palladium (t 4-Bicyclo[2.2.1]hepta-dien)-dimethyl- XIII/9b, 720... 

Cyclopropan-< piro-9>- 1101... 

Norbornadiene, (which is the preferred name for bicyclo[2.2.1]hepta-diene-2,5 (I), was first reported in the patent literature in 1951 (5). It is commercially available (e.g., from Matheson, Coleman and Bell) and usually manufactured from the reaction of acetylene with cyclopentadiene under pressure at temperatures between 230° and 320°. It may... 

Oxo-l,7-diphenyl-(benzo-6-oxa-bicyclo[3.1.0]hexen-(2)) in50 ml frisch destiliertem Bicyclo[2.2.1]hepta-dien wird in einem wassergekiihlten QuarzgefaB mit einer 100 W Quecksilber-Mitteldruck-Lampe 5 Stein, bestrahlt. AnschlicBend wird das iibersehiissige Bicyclo[2.2.1]heptadien i. Vak. entfernt und der Buck-stand mit 25 ml heiBem Athanol zerrieben Ausbeute 0,83 g (63% d.Th.) F 215-216° (Athanol). 

In the 1950s two very effective pesticides were launched and their names were Dieldrin and Aldrin. As you may guess they were made by the Diels-Alder reaction. Aldrin is derived from two consecutive Diels-Alder reactions. In the first, cyclopentadiene reacts with acetylene to give a simple symmetrical cage molecule norbornadiene (bicyclo[2.2.1]hepta-diene). Norbornadiene is not conjugated and cannot take part in a Diels-Alder reaction as a diene. However, it is quite strained because of the cage and it reacts as a dienophile with perchlorocyclopentadiene to give Aldrin. 

Bicyclo[2.2.1]hepta-2,5-diene rhodium (I) chloride dimer (norbornadiene rhodium chloride complex dimer) [12257-42-0] M 462, m 240°(dec). Recrystd from hot CHCl3-pet ether as fine crystals soluble in CHCI3 and C H but almost insoluble in Et20 or pet ether. [7 Chem Soc 3178 1959.]... 

In the Hiickel treatment, atomic orbitals on nonadjacent atoms are assumed to have no interacticai. They are neither bonding nor antibonding. The concept of homoconjugation suggests that such orbitals may interact, especially in rigid structures which direct orbitals toward one another. Consider, for example, bicyclo[2.2.1]hepta-2,S-diene ... 

An especially interesting case of the hexatriene-cyclohexadiene type interconversion is the rapid equilibrium between cycloheptatrienes and bicyclo[4.1.0]hepta-2,4-dienes ... 

Acetic acid, reaction with bicyclo[2.2,1]-hepta-2,5-diene, 45, 74 reaction with dibenzyl ketone, 47, 54... 

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... 

Bicyclo[2.2.1]hepta-2,5-diene, nitrosyl chloride adduct, 46, 74 reaction with acetic acid to yield nortricyclyl acetate, 46, 74 Bicyclohexyl, 46, 61 Bicyclohexylidene, 47, 34 ejSO-e s-BlCYCLO[3.3.0]OCTANE-2-CAR-BOXYLIC ACID, 47, 10 Bicyclopentadienylidene, octa-chloro-, 46,93... 

An essentially quantitative yield (98%) of the thermally stable hexafluoro-2-aza-bicyclo[3.2.0]hepta-3,6-diene 18 is obtained from the small-scale photolysis of the hexafluoro-l//-azepine 17.230 Hexafluoro-l//-azepine-l-carbonitrileand-l-carboxamidebehave similarly. On scaling up the process for the l-(ethoxycarbonyl) derivative 17, however, a much lower yield (59%) of bicycle 18 resulted, although this was improved to 81% by carrying out the photolysis in hexane or rm-butyl alcohol in the presence of a triplet sensitizer, e. g. ben-zophenone. 

The Dewar benzene of hexafluorobenzene formed an adduct with pheny-lazide that gave a polyfluoro-l//-azepine on pyrolysis. R=C02Et (47) was obtained when ethylazidoformate was decomposed in C6F6 [82JCS(P1)2101]. Photolysis of (47) yielded a 2-aza-bicyclo(3.2.0.)hepta-3,6-diene, which, in contrast to its nonfluorinated analogue, showed excellent thermal stability (3 h, 200°C, 88% recovered) [82JCS(P1 )2105]. 

Nickel-catalyzed [27t + 27t + 27r] (homo-Diels-Alder) and [27r-i-27r] cycloadditions of bicyclo[2.2.1 ]hepta-2,5-dienes [96]... 

Edman and Simmons [146] synthesized bicyclo[2.2.1]hepta-2,5-diene-2,3-dicar-boxylic anhydride 80 as a facially perturbed dienophile on the basis of the norbornadiene motif, and its top selectivity in Diels-Alder reactions with cyclopentadiene (top-exo top-endo = 60 70 1) was observed by Bartlett (Fig. 14) [147], The most preferred addition was top-exo addition, along with the minor addition modes, top-endo bottom-enrfo addition (Fig. 14). The addition of butadiene to this anhydride preferentially afforded the top-adduct (top bottom = 6 1). In the addition of anthracene, a top-adduct was formed exclusively. 

Homoconjugation results in enhanced reactivity of substrates toward ionic hydrogenation. Bicyclo[2.2.1]hepta-2,5-diene forms a mixture of the trifluoroac-etate esters of bicyclo[2.2.1]hepten-2-ol, tricyclo[2.2.1.02 6]heptan-3-ol, and bicyclo[2.2.1]heptan-2-ol in a 62 20 17 ratio on treatment with 10 equivalents of triethylsilane and 20 equivalents of trifluoroacetic acid for 24 hours at room temperature (Eq. 96), 230... 

Every example with a cyclohexene has proved hydrosilation to be very slow and difficult, but this difficulty was not experienced with cyclopen-tene structures by Petrov et al. (27). A number of chlorosilanes were added to bicyclo-(2,2,l)-hept-5-ene, bicyclo-(2,2, l)-hepta-2,5-diene, 2-methyl- and 2-vinylbicyclo-(2,2,l)-hept-5-ene, and dicyclopentadiene under mild conditions. Particularly surprising was the example of Eq. 

A 0-0 C3P-C3PS 2-Thia-l-phospha-bicyclo [3.2.0]hepta-3,6-diene 2, 493, 502 ... 

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