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Hafnium-Catalyzed Direct Amide Formation at Room Temperature
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
2015 (English)In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 5, no 6, 3271-3277 p.Article in journal (Refereed) Published
Abstract [en]

Herein, the first example of a metal-catalyzed protocol for direct amidation of non-activated carboxylic acids at ambient temperature (26 °C) is presented. The mild reaction conditions give rise to high yields of a range of amides in reaction times as short as 90 minutes, employing a commercial hafnium complex, [Hf(Cp)2Cl2], as catalyst. Amino acids are transformed into their corresponding amides without racemization, and the catalyst displays full selectivity for the amidation of carboxylic acids over esters. Electronic properties of the carboxylic acids were found to have a strong influence on the rate of the amidation reaction, and the need for a balanced amount of molecular sieves was observed to be highly important for optimal reaction outcome.

Place, publisher, year, edition, pages
2015. Vol. 5, no 6, 3271-3277 p.
Keyword [en]
hafnium, amidation, carboxylic acid, Lewis acids, catalysis
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-116889DOI: 10.1021/acscatal.5b00385ISI: 000355964300012OAI: oai:DiVA.org:su-116889DiVA: diva2:809424
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council
Available from: 2015-05-04 Created: 2015-05-04 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Group (IV) Metal-Catalyzed Direct Amidation: Synthesis and Mechanistic Considerations
Open this publication in new window or tab >>Group (IV) Metal-Catalyzed Direct Amidation: Synthesis and Mechanistic Considerations
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The amide unit constitutes the backbone of proteins, and it is present in a large number of pharmaceutically active molecules, polymeric materials such as nylon and Kevlar, as well as in food additives like aspartame. Amides are produced in enormous amounts every year, thus, environmentally friendly and selective methods for their formation are of great importance. This thesis deals with the direct formation of amides from non-activated carboxylic acids and amines with the aid of group (IV) metal complexes. Water is the only by-product of this environmentally benign process. This fact stands in contrast to the most common methods for amide formation to date, which involve the use of waste-intensive, expensive and often toxic coupling reagents. The catalytic protocols presented herein use titanium, zirconium and hafnium complexes under mild reaction conditions to produce amides in good to excellent yields. Furthermore, carbamates are demonstrated to be suitable sources of gaseous amines for the formation of primary and tertiary amides under catalytic conditions. In addition, preliminary results from on-going mechanistic investigations of the zirconium- and hafnium-catalyzed processes are presented.

Abstract [sv]

Amidbindningen är en kemisk enhet som utgör ryggraden i proteiner, och som även återfinns i en stor mängd läkemedelsmolekyler, polymera material som nylon och Kevlar, samt i tillsatser i livsmedelsindustrin, exempelvis aspartam. Amider produceras i enorma mängder varje år, och det är av stor vikt att utveckla miljövänliga och selektiva metoder för deras framställning. Denna avhandling behandlar direkt amidering av icke-aktiverade karboxylsyror och aminer med hjälp av katalytiska mängder metallkomplex, baserade på titan, zirkonium och hafnium. Den enda biprodukten från denna amideringsreaktion är vatten. Jämfört med de metoder som generellt används idag för amidsyntes, så är de presenterade metoderna avsevärt mer miljövänliga med avseende på toxicitet hos reagensen såväl som på mängden avfall som genereras. Dessutom redovisas här en katalytisk metod för syntes av primära och tertiära amider genom att använda olika karbamat som källa till gasformiga aminer, vilka annars kan vara praktiskt svåra att arbeta med. Preliminära resultat från en pågående mekanistisk studie av de zirkonium- och hafnium-katalyserade processerna är också inkluderade.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2015. 77 p.
Keyword
catalysis, amide, carboxylic acid, amino acid, titanium, zirconium, hafnium
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-116955 (URN)978-91-7649-163-8 (ISBN)
Public defence
2015-06-12, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Accepted.

Available from: 2015-05-21 Created: 2015-05-04 Last updated: 2015-06-24Bibliographically approved

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