Are any non-stereospecific 1,3-dipolar cycloadditions known? A revision

doi:10.1016/S0040-4039(00)98877-4

Tetrahedron Letters

Volume 26, Issue 42, 1985, Pages 5119-5122

Dedicated to Professor Hans Musso on the occasion of his 60th birthday

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Abstract

The cycloaddition of 1-benzylidenepyrazolid-3-one betaine to (E)-β-nitrostyrene, which has been claimed to furnish 15–30% non-stereospecific product, revealed stereospecificity up to 99.92% in a renewed study; (Z)-β-nitrostyrene stereoisomerizes under the influence of the 1,3-dipole.

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There are more references available in the full text version of this article.

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A novel and practical protocol for the synthesis of fully substituted pyrazoles from pyridinium 1,4-zwitterionic thiolates and hydrazonoyl chlorides in excellent yields under mild conditions is described. The transformation proceeds via an unusual [[3 + 3] − 1] pathway, which involves a formal [3 + 3] cascade cyclization followed by a spontaneous ring-contraction/sulfur extrusion reaction from 4H-1,3,4-thiadiazine intermediates.
The concern of emergence of multi-station reaction pathways that might make stepwise the mechanism of the 1,3-dipolar cycloadditions of azides and alkynes
2018, Journal of Molecular Structure
Citation Excerpt :
These all are admirable, but what could become a concern, is that in the recent years, some reports have revealed about the stepwise-character of the mechanism of 1,3-DC reactions. It is clear that; if the mechanism of a catalyst-free 1,3-DC reaction switches from concerted to stepwise, intermediates would evolve, the reaction would become non-stereospecific, and unwanted stereoisomers could yield as consequences [3]. Unlike some rare examples, especially for the cases of some thiocarbonyl ylides [4–6], and a few nitrile oxides [7,8], the mechanism of the catalyst-free 1,3-DC reactions of most 1,3-dipoles especially azides, are not practically believed to be stepwise [9,10].
After hot debates on the concerted or stepwise nature of the mechanism of the catalyst-free 1,3-dipolar cycloadditions (DC)s, nowadays, it is being believed that for the reaction of each dipole and dipolarophile, there is a possibility that the reaction mechanism becomes stepwise, intermediates emerge, and the reaction becomes non-stereospecific. Yield of even minimal amounts of unwanted side products or stereoisomers as impurities could bring many troubles like difficult purification steps.
In this project, we have made attempts to study all probable reaction channels of the azide cycloadditions with two functionalized alkynes, in order to answer this question: "is there any possibility that intermediates evolve in the catalyst-free click 1,3-DC reaction of azide-alkynes?". During the calculations, several multi-station reaction pathways supporting the stepwise and concerted mechanisms were detected. Also, the born–oppenheimer molecular dynamic (BOMD) simulation was used to find trustable geometries which could be emerged during the reaction coordinate.
Catalyst free 1,3-dipolar cycloaddition of 3-oxo-1,2-pyrazolidinium ylides to β-trifluoroacetyl vinyl ethyl ether: Synthesis of 6-trifluoroacetyl substituted bicyclic pyrazolidinones
2011, Journal of Fluorine Chemistry
Cycloadditions of two thiocarbonyl ylides with α,β-unsaturated esters and nitriles: Steric course and mechanism
2002, Tetrahedron
In the probably concerted cycloadditions of the sterically hindered thiocarbonyl ylide 1 with fumaronitrile, maleonitrile, and dimethyl fumarate, the dipolarophile configuration is retained whereas retention/inversion 99:1 for dimethyl maleate (51 times less reactive than fumarate) signals a small involvement of a two-step pathway. The latter becomes dominant when two acceptor groups stabilize the anionic terminus of a zwitterionic intermediate. Nonstereospecific cycloadditions of 1 with dimethyl 2,3-dicyanofumarate (16, retention/inversion 60:40) and dimethyl 2,3-dicyanomaleate (17, 76:24) were observed. Special conditions were required to avoid a preceding cis, trans isomerization, 16⇄17, catalyzed by thiadiazoline 4, the precursor of 1. In the case of the related thiocarbonyl ylide 37, this catalysis could not be suppressed and the same ratio of adducts (55:45) was obtained with 16 and 17.
Nonstereospecific 1,3-dipolar cycloadditions of azomethine ylides and enamines
1999, Tetrahedron
Nonstereospecific 1,3-dipolar cycloadditions - LUMO(dipole)-HOMO(dipolarophile) controlled reactions
1998, Tetrahedron Letters
FMO-theory predicts a two-step mechanism accompanied by nonstereospecificity for 1,3-dipolar cycloadditions if one HOMO-LUMO interaction dominates the other one. R. Huisgen proved this phenomenon for the combination of electron-rich thiocarbonyl ylides with electron-poor dipolarophiles. For the first time we report on nonstereospecific reactions of electron-poor 1,3-dipoles 1 and 5 with the electron-rich trans-enamine 2.

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¹: Diploma Thesis R. Weinberger, University of Munich, January 1984.

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Are any non-stereospecific 1,3-dipolar cycloadditions known? A revision

Abstract

J. Prakt. Chem.

Chem. Ber.

Angew. Chem., Int. Ed. Engl.