1,5-Elektrocyclisierungen – ein wichtiges Prinzip der Heterocyclen-Chemie

Huisgen, Rolf

doi:10.1002/ange.19800921204

Cited by 145 publications

(18 citation statements)

References 164 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The reaction of 5 with aqueous methanol gave only 11. Using [D4]methanol/D20 the rate of this transformation, which agreed with the rate of the NJ, 80 (32), 67 (12), 66 (12), 54 (58), 53 (51).…”

Section: -(L-mentioning

confidence: 50%

Reactions of Unsaturated Azides, 6. Synthesis of 1,2,3‐Triazoles from Propargyl Azides by Rearrangement of the Azido Group. – Indication of Short‐Lived Allenyl Azides and Triazafulvenes

Banert

1989

Chem. Ber.

View full text Add to dashboard Cite

Treatment of 3-bromo-3-methyl-I-butyne (1) or 1 4odo-3-methyl-13-butadiene (3) with solutions of sodium azide affords 3-azido-3-methyl-1-butyne (5) which reacts already at room temperature to 1,2,3-tn'azoles 8-11. Structures of 5 and 8-11 are verified by independent syntheses and spectroscopic data although in part other assignments of structures have been published. The preparation of 1 H-1,2,3-triazoles via propargyl azides is carried out in the presence of various nucleophiles and investigated by means of "N-labelled starting material as well as optically active 3-azido-I-butyne (R-21). The only mechanism compatible with all results includes short-lived allenyl azides and triazafulvenes. Thus, propargyl azide 14 rearranges to allenyl azide 16 leading to triazafulvene 18 by rapid ring closure. Finally, 18 is trapped by nucleophiles to give triazole 17. The conversion of various propargyl compounds into N-unsubstituted lH-1,2,3-triazoles 23,41,44,46, 50, and 51 is &&ed by a one-pot procedure without isolation of 14 and turns out to be a convenient method to prepare these heterocycles.Vinyl azides which are known for their manifold reactions can be synthesized by various methods". But all attempts to isolate allenyl azides -possible precursors for yet unknown alkylideneazirines -were unsu~cessful~~~). In a publication by Shiner and Humphrey, the authors claimed to have obtained the allenyl azide 4 together with the propargyl azide 5 from the reaction of bromides 1 or 2 with sodium azide in deuterated aqueous ethanol'). However, 4 and 5 were only characterized in the reaction mixture by their 'H-NMR data, because they decomposed already at room temperature to unknown products. Since the observation of 4 represents the only direct reference to an allenyl azide, detailed reinvestigations of the reaction of 1 with sodium azide in aqueous alcohols are now presented. 1,2,3-Triazoles from 3-Azido-3-methyl-1-butyne (5)Treatment of 1 6.7) with sodium azide in aqueous ethanol at first gives only the propargyl azide 5, which subsequently produces the triazoles 8 -los, along with the other solvolysis products, 2-methyl-l-buten-3-yne, 2-methyl-3-butyn-2-01, and 12. NMR data indicate that 9 was taken for 3 in the literature, that 5 was correctly recognized, and that 8 and 10 are the succeeding products not identified by Shiner and Humphrey'). If the reaction is carried out using deuterated solvents the allenyl azide 4 cannot be detected by 'H-NMR spectroscopy. With sodium azide in aqueous methanol, 1 or the less reactive 37.'0' similarly furnish 5 and subsequently 8, 9, and 11. Due to the formation of several solvolysis products'the triazoles are isolated in low yields (16% of 9 and 16% of 11 based on 1). Using sodium azide in aqueous acetone affords only 8 and 9 as final triazoles (43% yield based on 1). Although the azide 5 is very unstable at room temperature it can be isolated from 3 and hexadecyltributylphosphonium azide (QN3) * I ) in 44% yield. With sodium azide in aqueous alcohols, 5 produces 8 and 9 as well as 10 or 1...

show abstract

Section: -(L-mentioning

confidence: 50%

Reactions of Unsaturated Azides, 6. Synthesis of 1,2,3‐Triazoles from Propargyl Azides by Rearrangement of the Azido Group. – Indication of Short‐Lived Allenyl Azides and Triazafulvenes

Banert

1989

Chem. Ber.

View full text Add to dashboard Cite

show abstract

“…This powerful acid-mediated reaction was originally discovered by Fischer, and Huisgen later noticed the isoelectronic relationship between this transformation and the 6p electrocyclization of the pentadienyl anion (Scheme 1). [7,8] Although truly catalytic versions of Fischers pyrazoline synthesis are scarce, we reasoned that a chiral Brønsted acid catalysis strategy might be applicable. Herein we show that such catalysis is indeed possible and report what is, to our knowledge, the first catalytic asymmetric 6p electrocyclization.…”

mentioning

confidence: 99%

A Catalytic Asymmetric 6 π Electrocyclization: Enantioselective Synthesis of 2‐Pyrazolines

2009

View full text Add to dashboard Cite

“…The behavior of SCS-MP2 in calculating the activation energies for these electronically difficult to describe reactions is far better ( Electrocyclization reactions: Interconverting cyclic and acyclic compounds by electrocyclic processes represents another class of pericyclic reactions that is important to preparative organic chemistry. [30] Besides the ubiquitous ring-opening and -closing reactions of neutral systems with an even number of participating atoms, there are also numerous examples of cations and anions with an odd number of participating atoms that undergo these reactions. Like the cycloadditions and sigmatropic rearrangements, many electrocyclizations are known in which a heteroatom is involved.…”

mentioning

confidence: 99%

Improved Reaction and Activation Energies of [4+2] Cycloadditions, [3,3] Sigmatropic Rearrangements and Electrocyclizations with the Spin‐Component‐Scaled MP2 Method

Goumans

Ehlers

Lammertsma

et al. 2004

Chemistry A European J

View full text Add to dashboard Cite

A new quantum mechanical scheme to calculate electronic correlation energies, spin-component-scaled MP2, was tested as a tool to predict reaction energies and barriers in computational organic chemistry. Three common pericyclic reactions with known unsatisfactory MP2 descriptions were reinvestigated with the modified MP2 approach, in which the parallel and anti-parallel spin components of the correlation energy are scaled separately. The SCS-MP2 calculated reaction and activation energies of nine Diels-Alder reactions, four [3,3] sigmatropic rearrangements, and ten electrocyclization reactions are compared to those of the MP2, B3 LYP, QCISD(T), and G3 methods. For each, the SCS-MP2 results are in excellent agreement with the experimental data and compare far more favorably to G3 than both MP2 and B3 LYP. Careful evaluation of the effect of the size of the atomic orbital (AO) basis set shows that the larger expansions improve the agreement with experiment for the SCS-MP2 method, while they get worse for both MP2 and B3 LYP.

show abstract

1,5-Elektrocyclisierungen – ein wichtiges Prinzip der Heterocyclen-Chemie

Cited by 145 publications

References 164 publications

Reactions of Unsaturated Azides, 6. Synthesis of 1,2,3‐Triazoles from Propargyl Azides by Rearrangement of the Azido Group. – Indication of Short‐Lived Allenyl Azides and Triazafulvenes

Reactions of Unsaturated Azides, 6. Synthesis of 1,2,3‐Triazoles from Propargyl Azides by Rearrangement of the Azido Group. – Indication of Short‐Lived Allenyl Azides and Triazafulvenes

A Catalytic Asymmetric 6 π Electrocyclization: Enantioselective Synthesis of 2‐Pyrazolines

Improved Reaction and Activation Energies of [4+2] Cycloadditions, [3,3] Sigmatropic Rearrangements and Electrocyclizations with the Spin‐Component‐Scaled MP2 Method

Contact Info

Product

Resources

About