Norbomanes—

Low temperature fluorination techniques (—78° C) are promising for the preparation of complex fluorinated molecules, especiaUy where functional groups are present (30), eg, fluorination of hexamethjiethane to perfluorohexamethylethane [39902-62-0] of norbomane to perfluoro- (CyF 2) 1-hydro undecafluoronorbomane [4934-61 -6] C HF, and of adamantane to 1-hydropentadecafluoroadamantane [54767-15-6]. 

X-r crystal structure determinations have been completed on two salts containing bicyclo[2.2.1]heptyl cations (Fig. 5.12). Both are more stable than the 2-norbomyl cation itself 18 is tertiary whereas 19 contains a stabilizing methoxy group. The crystal structure of 18 shows an extremely long (1.74 A) C—C bond between C-1 and C-6. The C(1)—C(2) bond is shortened to 1.44 A. The distance between C-2 and C-6 is shortened from 2.5 A in norbomane to 2.09 AThese structural changes can be depicted as a partially bridged structure. 

Substituted norbomanes, such as camphor, aTe found widely in nature, and many have been important historically in developing organic structural theories. 

Recently a reverse perturbation effect of a cyclopropyl group on facial selectivities was described in two bicyclic systems, bicyclo[2.2.2]octane 59 and norbomane (bicyclo[2.2.1]heptane) 60 [124]. Bicyclo[2.2.2]octene 59a, annulated with an exo-cyclopropyl group, i.e., exo-tricyclo[3.2.2.0 ]non-6-ene, and 7-methylenenor-bomane 60a, annulated with an exo-cyclopropyl group, i.e., 8-... 

The anti facial preference of the norbomane 60a was previously found in the additions of dichlorocarbene (syn anti = 44 56) [125, 126] and of 9-BBN (symanti = 11 89) [125, 126]. The anti-preference was also observed in the reactions of methylidenebicyclo[2.2.1]heptane (60b) bearing an enrfo-dimethylcyclopropyl group (Rj,R2=C(CH3)2) [125, 126] with dichlorocarbene (symanti = 34 66) and 9-BBN (syn anti = 5 95). Therefore, we can conclude that the anti-preference, induced by a cyclopropyl group, is intrinsic to 7-methylidenenorbomane 60a. The anti preference was also observed in alkyl-substituted 46d (R = Rj = Et), supporting the idea that a cyclopropyl group behaves as an electron-donating substituent [78]. 

Although there have been many experimental and theoretical studies on the behavior of facially perturbed dienes (see below), only a few systematic experiments have been carried out to characterize facially perturbed dienophiles. Dienophiles embedded in the norbomane or norbomene motif have been rather intensively studied [146-150]. In most cases, steric effect controls selectivity, but in some cases the reactions are considered to be free from steric bias, and the selectivity has been explained in terms of other factors, such as orbital effects [151, 152]. 

Aydin, R., Gunther, H. C, H spin-spin coupling. 9. Norbomane a reinvestigation of the Karplus curve for... 

The Diels-Alder reaction between oxazolone and cyclopentadiene in water was investigated by Cativiela (Eq. 12.35).96 Although the reaction is very slow, the ( )-5(4H)-oxazolone reacted with cyclopentadiene in an aqueous medium for six days at room temperature to form the corresponding sprioxazolones in a 95% yield. The cycloadducts were then readily converted into amino-norbomane carboxylic acids. 

The reactivity of hydrogens in norbomane towards abstraction is of interest since the difference between two hydrogen atoms attached to the same carbon atom of position 2 can well be explained. The frontier electron density values 105> are in accord with the reactive exo hydrogen (Fig. 7.20). 

Finally, it is important to mention that there are other related publications in which porphyrin macrocycles are not directly used as dipolarophiles but are transformed into new derivatives that can react with carbonyl ylides via ACE (alkene cyclobutene epoxide) reactions. This idea arose in 1997, when Russell and co-workers found that fused ester-activated cyclobutene epoxides 86 can be ring-opened to give carbonyl ylides 87, and that these can be trapped stereospecifically by ring-strained alicyclic dipolarophiles, such as 2,5-norbomadiene, to form hetero-bridged norbomanes 88 in good yields, through ACE transformations (Scheme 31) <97CC1023>. 

The aziridine-coupling reaction had the ability to introduce bridge-substituents X or Y on either side of the iV-bridge in fused 7-azanorbomanes 87 and allowed a rare opportunity to study through-space effects on A-bridge hybridisation and JV-alkyl invertomerisation in fused 7-aza norbomanes. 

The JV-benzyl aziridines 69, 92-95 which differ only in the nature of the norbomane bridge (CH2, spirocyclopropyl, isopropylidene, oxygen, substituted nitrogen) (Scheme 14), have been prepared and reacted with each of the corresponding benzonorbomadienes 36-40 from which they were derived. All 25 reactions were conducted to produce 14 of the possible 15 different... 

Early studies with a purified and reconstituted rabbit P450, CYP2B4 (earlier name P450 LM2) on the hydroxylation of the hydrocarbon, norbomane, found that the reaction proceeded to yield a 3.4 1 mixture of exo-endo norborneols (4). Further, hydroxylation of exo-2,3,5,6-tetradeuteronorbornane was found to proceed with a large deuterium isotope effect (11.5 0.5) and a significant amount of epimerization in forming the endo and exo metabolites (Fig. 4.3). 

Norbomane, hydrogenolysis, 30 64-65 Norbomene, metathesis of, 24 136 Norcamphene, isomerization of, 20 271 Nozieres-De Dominicis many-body effect, 34 247... 

Norbomane [279-23-2] Daphnia pulex EC50 (48-h) 0.72 Passino-Reader et ah, 1997... 

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