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Intermolecular Pummerer Coupling with Carbon Nucleophiles in Non-Electrophilic Media
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.ORCID iD: 0000-0001-9199-6736
Number of Authors: 32017 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 56, no 50, p. 16042-16046Article in journal (Refereed) Published
Abstract [en]

A new Pummerer-type C-C coupling protocol is introduced based on turbo-organomagnesium amides, which unlike traditional Pummerer reactions, does not require strong electrophilic activators, engages a broad range of C(sp(3))-, C(sp(2))-, and C(sp)-nucleophiles, and seamlessly integrates with C-H and C-X magnesiation. Given the central character of sulfur compounds in organic chemistry, this protocol allows access to unrelated carbonyls, olefins, organometallics, halides, and boronic esters through a single strategy.

Place, publisher, year, edition, pages
2017. Vol. 56, no 50, p. 16042-16046
Keywords [en]
C-C coupling, magnesium, main group elements, Pummerer reaction, sulfur
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-150977DOI: 10.1002/anie.201709715ISI: 000417200600045PubMedID: 29053208OAI: oai:DiVA.org:su-150977DiVA, id: diva2:1173407
Available from: 2018-01-12 Created: 2018-01-12 Last updated: 2018-10-01Bibliographically approved
In thesis
1. New C-C coupling Reactions Enabled by Main-group Organometallics
Open this publication in new window or tab >>New C-C coupling Reactions Enabled by Main-group Organometallics
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The carbon-carbon bond has always been at the very core of chemical research. Strategies for the creation of C−C bonds are one of the keys to the construction game that organic chemists play with the building blocks provided by Nature, with the ultimate goal of producing useful molecular structures that will serve society as medicines, materials, imaging tools, catalysts, and ligands (to mention but a few). While very different in their structure, all of these molecules are often prepared by the same methods. However, efficiency could be improved with tailored chemical strategies that would serve an individual purpose. Ideally, these chemical manipulations should be efficient, selective, environmentally friendly and economic, in order to truly fulfill their final objective.

However, despite the ever-expanding rule-book of chemical reactions, target molecules of increasing complexity often face chemists with daunting challenges, whose success rely on multi-step synthetic sequences. There is therefore a permanent need for new, specific methods and strategies that are capable of seamlessly creating C−C bonds, evading the synthesis of difficult or expensive substrates. In this regard, common organometallic reagents display a unique behavior as carbon precursors, in particular as powerful nucleophiles. Reagents based on main-group elements such as lithium or magnesium have therefore played a central role in organic synthesis ever since their discovery. The challenge often lies in controlling their high reactivity, as well as their basic character. Tuning and taming these properties provides chemists with a wide range of unique strategies for the selective synthesis of countless molecular targets.

In the first part of this thesis, a scalable and stereoselective [3+3] homocoupling of imines in which two C−C bonds are formed in a single step is reported. This reaction relies on an unusual combination of visible-light irradiation and aluminum organometallics. This photochemical process enables the circumvention of the native [3+2] reactivity of these readily available starting materials, thus enabling rapid access to densely functionalized piperazines. Thanks to the congested environment they provide, these heterocyclic scaffolds can be used as ligands to prevent catalyst deactivation through oligomerization.

The next chapter presents a novel Pummerer-type redox-neutral coupling of sulfoxides and Grignard reagents. This reaction is enabled by a unique turbo-magnesium amide base, and allows the use of a wide range of carbon nucleophiles in intermolecular Pummerer C−C coupling for the streamlined preparation of thioethers. Given the central character of sulfur in organic chemistry, these compounds can then be converted to a variety of unrelated functional groups for the streamlined preparation of diverse building blocks.

In the final two chapters, the development of a method for the direct conversion of carboxylic acids to ketones with Grignard reagents is described. Using the above-mentioned combination of organometallics, a wide variety of carboxylic acids substrates and Grignard reagents can be coupled in a convenient, scalable and highly selective method that suppresses the need for activation and offers a straightforward approach to ketones from readily available starting materials.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2018. p. 82
Keywords
C-C coupling, organometallics, aluminum, magnesium, Grignard, turbo-Hauser-bases, piperazines, sulfur, ketones
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-160658 (URN)978-91-7797-418-5 (ISBN)978-91-7797-419-2 (ISBN)
Public defence
2018-11-16, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.

Available from: 2018-10-24 Created: 2018-10-01 Last updated: 2018-10-24Bibliographically approved

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