2.3- Dichloro-2-norbornene

Early work involving simple alkenes employed the catalyst dichloro (y )-AUV-dimethyl-l-[(S)-2-(diphenylphosphino)ferrocenyl]ethylamine palladium(II), 1 (often abbreviated to Pd-Cl2[(i )-(S)-PPFA]). When applied to the hydrosilylation of norbornene with trichlorosilane, it yielded an adduct which was converted to a pentafluorosilicate and thence to the alcohol 2 in 25% overall yield and with 50% ee26. 

Partial reduction of dichloro(norbomadiene)palladium with sodium borohydride at — 40 C gave an intermediate 25 which could not be isolated but was assumed to be a homoallyl complex which upon reductive cleavage gave norbornene, norbomane and nortricyclene in a ratio of 9 7 1, while oxidative decomplexation gave norbornenone and nortricyclenone in a 1 1 ratio. ... 

Traylor et al. reached different conclusions in studies of alkene epoxidation. In homogeneous solutions in which iodosylbenzene was solubilized in dichloro-methane/alcohol/water, very rapid epoxidation (300 turnovers/sec) was found to be independent of substrates or concentration of alkane (124). No dependence on alkene concentrations was reported by Dicken et al. when they employed /7-cyanodimethylaniline 7V-oxide (725). Meanwhile, Traylor et al. found an accumulation of 7V-alkyliron porphyrin complexes (35) during the course of epoxidation of norbornene (126), and showed that it is the only intermediate accumulated in either the homogeneous system or the heterogeneous system 35 was found to form with a bimolecular rate constant of 450 M sec and decomposes at a rate of 0.07 sec. Epoxide formation occurs with a rate constant of at least 10 Af" sec in these conditions. Thus 35 is not an intermediate in the production of epoxide however, it could account for at least a small percentage of the products, since 35 was found to catalyze alkene epoxidation by utilizing PhIO (Scheme XIX). 

Diels-Alder addition of tetrachlorocyclopentadiene dimethylketal to endo-5-norbornene carboxylic acid produces (459). Ketal cleavage (H2SO4), cheletropic loss of CO (reflux in o-dichloro benzene), and aromatization (bromine in hot chlorobenzene) affords the endo-acid (460 X = Cl) which can be dechlorinated by reaction with Ni-Al alloy and alkali to give (460 X = H). The clean retention of stereochemistry in reaction sequence is suggested to be of value in the general synthesis of alicyclic-substituted benzonorbornenes the methyl ester of (460 X = H) can likewise be prepared without epimerization. ... 

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