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Norbornadiene

About: Norbornadiene is a research topic. Over the lifetime, 2389 publications have been published within this topic receiving 38603 citations.


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TL;DR: The cobalt catalyzed neutral Diels-Alder reaction of various acyclic 1,3-dienes and norbornadiene with 1, 3-diynes can be controlled to give the 1:1 adduct, whereas the 1 : 2 adducts are only formed with sterically less hindered 1.3-Dienes as discussed by the authors.
Abstract: The cobalt catalyzed neutral Diels-Alder reaction of various acyclic 1,3-dienes and norbornadiene with 1,3-diynes can be controlled to give the 1:1 adduct, whereas the 1:2 adducts are only formed with sterically less hindered 1,3-dienes. With unsymmetrical 1,3-diynes the regiochemistry is mainly controlled by steric factors for unfunctionalized diynes, whereas the regiodirecting methoxymethyl substituent favors the Diels-Alder reaction at the closest triple bond. The combination of steric effects and the methoxymethyl substituent exclusively generates one of the two possible neutral Diels-Alder products. The mild oxidation of the dihydroaromatic products by stoichiometric amounts of DDQ, or alternatively under electrochemical regeneration of the spent oxidizing agent at the anode, generates phenylacetylene derivatives, from the 1:1 adduct, or biphenyl derivatives, from the 1:2 adducts respectively.

27 citations

Journal ArticleDOI
TL;DR: In this paper, bidentate heterocyclic chelating ligands (LL) have been used to generate diolefin neutral, ionic or ion-pair type compounds depending on the ligands and/or the ratio employed.
Abstract: Cleavage of [{Rh(diolefin)Cl}2] by bidentate heterocyclic chelating ligands (LL) has been studied, and diolefin neutral, ionic or ion-pair type compounds are formed depending on the ligands and/or the Rh: (LL) ratio employed. When the reactions are performed in media saturated with CO and with Rh: (LL)=2∶1, only carbonylated ion-pair complexes are formed. The diolefin compounds react with tin(II) chloride yielding species containing trichlorostannato-groups. Subsequent reaction with CO leads to displacement of the diolefin and formation of the corresponding dicarbonyl species.

27 citations

Journal ArticleDOI
TL;DR: The crystal structure of 9a, determined in addition to the solution structure elucidation by multinuclear NMR spectra, confirms the chelate formation and reveals a trigonal environment for the low coordinated phosphorus.
Abstract: Acid-catalyzed cyclocondensations of 2-phosphanylanilines 1 with substituted benzaldehydes or heteroaryl aldehydes open a convenient route to new biaryl-type 1H-1,3-benzazaphosphole hybrid ligands 2a–f with o-phosphanylphenyl, pyridyl, imidazolyl, thienyl or o-methoxyphenyl donor groups (in addition to the σ2P donor) and to bromophenyl substituted benzazaphospholes 2g,h. Excess aldehyde leads to concomitant reductive N-alkylation, as shown by formation of 3h besides 2h. The reactions proceed via dihydrobenzazaphospholes 4, which can be detected under mild conditions. The aromaticity-driven dehydrogenation does not liberate dihydrogen but is accomplished by transfer hydrogenations, mainly by reduction of some of the aldehyde. N-Secondary 2-phosphanylanilines 5 also react with aldehydes to form the corresponding N-substituted benzazaphospholes 6. The formation of (P^P′)M(CO)4-chelate complexes 8a (M = Cr) and 9a,b (M = Mo) was demonstrated by reaction with M(CO)4(norbornadiene). The crystal structure of 9a, determined in addition to the solution structure elucidation by multinuclear NMR spectra, confirms the chelate formation and reveals a trigonal environment for the low coordinated phosphorus, with the P–Mo(0) vector bent out of the benzazaphosphole ring plane by 14.4° (0.57 A), together with axial chirality of the molecules in the racemic crystals by twisting of the benzazaphosphole and phenyl π-planes around the common C(2)–C(21) bond.

27 citations

Journal ArticleDOI
TL;DR: The crystal structures of 6+ PF6- and 12+PF6- are compared to those of 3 and 9, and other rhodium complexes of chelating bis(diphenylphosphines).
Abstract: The title compounds are accessed by sequences starting with racemic and enantiomerically pure [(eta5-C5H5)Re(NO)(PPh3)(CH3)]. Reactions with chlorobenzene/HBF4, PPh2H, and tBuOK give the phosphido complex [(eta5-C5H5)Re(NO)(PPh3)(PPh2)] (3). Reactions with Ph3C+ BF4-, PPh2H, and tBuOK give the methylene homologue [(eta5-C5H5)Re(NO)(PPh3)(CH2PPh2)] (9). Treatment of 3 or 9 with nBuLi or tBuLi and then PPh3Cl gives the diphosphido systems [(eta5-C5H4PPh2)Re(NO)(PPh3)((CH2)nPPh2)] (n = 0/1, 5/11). Reactions of 5 and 11 with [Rh(NBD)Cl]2/AgPF6 (NBD = norbornadiene) give the rhenium/rhodium chelate complexes [(eta5-C5H4PPh2)Re(NO)(PPh3)((mu-CH2)nPPh2)Rh(NBD)]+ PF6- (n = 0/1, 6+/12+ PF6-; 30-32% overall from commercial Re2(CO)10). The crystal structures of 6+ PF6- and 12+ PF6- are compared to those of 3 and 9, and other rhodium complexes of chelating bis(diphenylphosphines). The chiral pockets defined by the PPh2 groups show unusual features. Four alkenes of the type (Z)-RCH=C(NHCOCH3)CO2R' are treated with H2 (1 atm) and (R)-6+ PF6- or (S)-12+ PF6- (0.5 mol%) in THF at room temperature. Protected amino acids are obtained in 70-98% yields and 93-82% ee [(R)-6- PF6-] or 72-60% ee [(S)-12+ PF6-]. Pressure and temperature effects are defined, and turnover numbers of > 1600 are realized.

27 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202316
202240
202133
202040
201930
201829