Topic
Norbornene
About: Norbornene is a research topic. Over the lifetime, 5628 publications have been published within this topic receiving 104495 citations. The topic is also known as: norbornylene & norcamphene.
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TL;DR: In all cases, attack of the N-arylimine dienes occurred exclusively from the exo-face of the norbornene ring, but the relative stereochemistry of the substituent alpha to the tetrahydroquinoline nitrogen, as well as the regioselectivity of reaction, was shown to depend upon subtle substituents effects on the aniline precursors.
Abstract: Generally, the hetero-Diels−Alder reaction (Povarov reaction) of N-arylimine dienes are limited to reaction with activated, electron-rich alkenes. However, introduction of ring strain in the dienophile, as with moderately strained bicyclo[2.2.1]heptenes (norbornene), enables three-component Povarov reaction with in situ formed N-arylimines under Lewis acid catalyzed conditions (BF3·OEt2). The reactions proceed efficiently with a diverse set of commercially available anilines and benzaldehydes, as well as a variety of substituted norbornenes. The corresponding tetrahydroquinolines are formed with high complexity in a multicomponent fashion and are obtained in good yield and high diastereoselectivity. In addition, more reactive ethyl glyoxylate derived imines were utilized to achieve faster, room temperature reactions with norbornene. In all cases, attack of the N-arylimine dienes occurred exclusively from the exo-face of the norbornene ring, but the relative stereochemistry of the substituent α to the tetr...
72 citations
TL;DR: The oxanickelacyclopentanone-derivate (I) can easily be prepared from norbornene (bicyclo[2.2.1]heptene), CO2 and nickel(0) compounds.
72 citations
72 citations
TL;DR: In this article, the authors deduced that β-Diketiminato (BDI) calcium alkyl derivatives undergo hydrogenolysis with H2 to regenerate [(BDI)-CaH]2, allowing the catalytic hydrogenation of a wide range of 1-alkenes and norbornene under very mild conditions (2 bar H2, 298 K).
Abstract: β-Diketiminato (BDI) calcium alkyl derivatives undergo hydrogenolysis with H2 to regenerate [(BDI)CaH]2 , allowing the catalytic hydrogenation of a wide range of 1-alkenes and norbornene under very mild conditions (2 bar H2 , 298 K). The reactions are deduced to take place with the retention of the dimeric structures of the calcium hydrido-alkyl and alkyl intermediates via a well-defined sequence of Ca-H/C=C insertion and Ca-C hydrogenation events. This latter deduction is strongly supported by DFT calculations (B3PW91) performed on the 1-hexene/H2 system, which also indicates that the hydrogenation transition states display features which discriminate them from a classical σ-bond metathesis mechanism. In particular, NBO analysis identifies a strong second order interaction between the filled α-methylene sp3 orbital of the n-hexyl chain and the σ* orbital of the H2 molecule, signifying that the H-H bond is broken by what is effectively the nucleophilic displacement of hydride by the organic substituent.
72 citations
TL;DR: A correlation of cycloaddition rates with substrate distortion was found for the bicyclic and tricyclic alkenes studied here, and the stereoselectivities of reactions of norbornene derivatives are controlled primarily by torsional effects that also influence alkene pyramidalization.
Abstract: The transition structures for 1,3-dipolar cycloadditions of phenyl azide to norbornene derivatives were located with quantum mechanical methods. Calculations were carried out with M06-2X/6-311G(d,p) and SCS-MP2/6-311G(d,p)//M06-2X/6-311G(d,p) methods. The calculated activation barriers strongly correlate with transition state distortion energies (ΔEd⧧) but not with the reaction energies. Strain-promoted reactions are accelerated because it is easy to distort the strained reactants to a pyramidalized transition state geometry; a correlation of cycloaddition rates with substrate distortion was found for the bicyclic and tricyclic alkenes studied here. The stereoselectivities of reactions of norbornene derivatives are controlled primarily by torsional effects that also influence alkene pyramidalization. These reactions are distortion-accelerated.
72 citations