First Enantioselective Catalytic Diels−Alder Reaction of Dienes and Acetylenic Aldehydes:  Experimental and Theoretical Evidence for the Predominance of <i>Exo</i>-Transition Structure

“…However, exo-endo selectivity of the reactions of acetylenic dienophiles was difficult to investigate, since exo and endo transition states produce diastereomerically identical adducts. Ishihara and Yamamoto [56,57] reported the first example of an enantioselective Diels-Alder reaction of acetylenic dienophiles with dienes, which have prochiral reactive centers, in the presence of chiral boron Cu(II) catalysts. The secondary orbital interaction is antibonding between the lobes on the 2-position of the dienes and carbonyl oxygen of the dienophiles (Scheme 12).…”

Section: Exo-addition In Diels-alder Reactionsmentioning

confidence: 99%

A Mechanistic Spectrum of Chemical Reactions

Inagaki

2009

Orbitals in Chemistry

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The mechanism of chemical reactions between electron donors and acceptors continuously changes with the power of the donors and the acceptors. The interaction between the HOMO (d) of the donors and the LUMO (a*) of the acceptors or delocalization of electrons is important for the reactions. The electron d-to-a* transferred configuration mixes to a significant extent. As the donors and/or the acceptors are strong, their excited configurations appreciably mixes together with the transferred configuration. The d-a and d*-a* orbital interactions are important in addition to the d-a* interaction. Reactions have features characteristic of the excited-state reactions although the donor-acceptor system is not really excited, but in the ground state. This process is termed pseudoexcitation. The a-d-a*-d* interaction is important. For much stronger donors and acceptors, the electron transferred configuration is stable and predominant. Covalent bonds do not form but instead ionic pairs, and electron transfer results. A mechanistic spectrum of chemical reactions is composed of the delocalization, pseudoexcitation, and electron transfer bands.

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“…Chiral Lewis acid systems such as certain boron catalysts (17) or organoaluminum compounds( 18) are even known to promote enantioselective cycloadditions. Despite the broad applicability of various transition metals as catalysts for cycloadditions, they sometimes give raise to unexpected, yet versatile reactions as they often change the electronic situation of llic entire system.…”

Section: Introductionmentioning

confidence: 99%

Chiral Chelating Systems: Unusual Formation and X-Ray-Structure of Rac-3a(r),4(s),5,9b(s)-Tetrahydro-4-(Pyrid-2-Yl)-3h-Cyclopenta[c]quinoline

Wurst¹,

Buchmeiser²

1999

Heterocyclic Communications

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N-Phenyl-2-(pyrid-2-yl)imine reacts with zinc iodide to give the corresponding diiodo zinc imine complex 1. I reacts with cyclopentadiene (CPD) at 0°C under ultrasound-assisted conditions to yield rac3a(R),4(S),5,9b(S)-tetrahydro-4-(pyrid-2-yl)-3//-cyclopenta[c]quino-line 2 instead of N-phenyl-5-aza-6-pyrid-2-ylnorborn-2-ene. The starting imine reacts with CPD in the same way yet more smoothly using BF, Et,0. With both Lewis-acids, the reaction proceeds regio-and distereoselectively. 1 crystallizes in the centrosymmetric space group Pi, a = 8.127 (1), b = 9.133(1), c = 10.467(1) A,"a = 104.36(1)°, β = 100.35(1)°, γ= 95.93(1)°V = 731.4(1) Ä\ Ζ = 2. 2 crystallizes in the centrosymmetric space group P2,/c. a = 10.559(3)), b = 15.061(2), c = 8.252(1) Α, β = 95.90(2)°, V = 13054(4) A 3 , Ζ = 4.

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First Enantioselective Catalytic Diels−Alder Reaction of Dienes and Acetylenic Aldehydes: Experimental and Theoretical Evidence for the Predominance of Exo-Transition Structure

Cited by 79 publications

References 12 publications

Theoretical Calculations of Metal‐Catalyzed Cycloaddition Reactions

Theoretical Calculations of Metal‐Catalyzed Cycloaddition Reactions

A Mechanistic Spectrum of Chemical Reactions

Chiral Chelating Systems: Unusual Formation and X-Ray-Structure of Rac-3a(r),4(s),5,9b(s)-Tetrahydro-4-(Pyrid-2-Yl)-3h-Cyclopenta[c]quinoline

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