Acceleration of ortho ester Claisen rearrangement by a commercial microwave oven

Srikrishna, A.; Nagaraju, S.

doi:10.1039/p19920000311

Cited by 44 publications

(19 citation statements)

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“…In our laboratory, identical reaction mixtures of geraniol, triethyl orthoacetate, propanoic acid and DMF were heated both conventionally and with MW at the boiling point of DMF for 10 min, but in contrast to the previous report, no significant rate enhancement was observed [19]. It should be pointed out that it is not clear whether identical reaction mixtures or the same temperatures had been used for the two heating methods in the previous report [42].…”

Section: Other Reactions In Polar Solventsmentioning

confidence: 49%

“…Substantial rate enhancements of over 100 times have been reported in ortho-ester Claisen rearrangements of allylic alcohols in DMF in open vessels [42]. For example, geraniol 25 gave an 87 % yield of the ester 26 in 12 min in a domestic MW oven, whereas the same reaction required 48 h of conventional heating to give a comparable yield (Scheme 4.14).…”

Section: Other Reactions In Polar Solventsmentioning

confidence: 94%

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Organic Synthesis Using Microwaves in Homogeneous Media

Gedye

2002

Microwaves in Organic Synthesis

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Although the ability of microwaves (MW) to heat water and other polar materials has been known for half a century or more, it was not until 1986 that two groups of researchers independently reported the application of MW heating to organic synthesis. Gedye et al. [1] found that several organic reactions in polar solvents could be performed rapidly and conveniently in closed Teflon vessels in a domestic MW oven. These reactions included the hydrolysis of amides and esters to carboxylic acids, esterification of carboxylic acids with alcohols, oxidation of alkyl benzenes to aromatic carboxylic acids and the conversion of alkyl halides to ethers.Most of these reactions occurred much faster using MW irradiation (at increased pressure and temperature) than under conventional heating (ambient pressure, reflux), with rate enhancements ranging from 5 to 1200 times.Shortly after these results were published, Giguere and coworkers reported dramatic reductions in reaction times in other MW-assisted syntheses, including Diels± Alder, Claisen rearrangements and ene reactions [2]. These reactions were also performed at elevated pressures, but sealed glass vessels (inside a bath packed with vermiculite) were used rather than Teflon.It is to be noted that the reactions mentioned so far were performed under homogeneous conditions and, in most cases, using polar solvents, which are efficient absorbers of MW energy. Rate enhancements were attributed to the superheating of the solvent due to the elevated pressures generated in the closed vessels.During the 15 years since these reports, a large number of synthetic applications of MW in organic. synthesis have been reported and these have been summarized in a number of reviews [3±10].The use of dry media (solvent-free) conditions, in which the reactants are absorbed on inert solid supports, in MW-heated reactions, has received a considerable amount of attention recently and has been used in the synthesis of a wide range of compounds [11±16]. These reactions generally occur rapidly and the method avoids hazards, such as explosions, associated with reactions in solvents in sealed vessels in which high pressures may be generated. Also the removal of 115 Microwaves in Organic Synthesis. Edited by Andr Loupy

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Section: Other Reactions In Polar Solventsmentioning

confidence: 49%

Section: Other Reactions In Polar Solventsmentioning

confidence: 94%

Organic Synthesis Using Microwaves in Homogeneous Media

Gedye

2002

Microwaves in Organic Synthesis

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“…It has been reported that certain reactions such as Diels-Alder [15,16], ethenoid [17], Claisen reaction [18], Fischer cyclization [19], synthesis of heterocycles [20], hydrolysis of esters [21,22], phosphoanhydride [23] and adenosine triphosphate formation [24], rapid hydrogenation [25], deprotection of benzyl esters [26], deacetylation of diacetates [27], Graebe-Ullmann synthesis [28], oxazoline formation [29,30], Knoevengel condensation [31], and aromatic ether formation [32,33] could be facilitated by microwave irradiation. However, to the best of our knowledge, no such application has been devised for the previously described Mannich-type reaction.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of cyclic esters of N-toluenesulfonyl ?-aminophosphonic acid

Dai

Chen

1998

Heteroatom Chem.

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“…Microwave irradiation has been used to effect organic reactions such as pericyclic [2], cyclization [3], aromatic substitution [4], oxidation, [5] alkylation [6], decarboxylation [7], radical reactions [8], condensation [9], and peptide synthesis [10].…”

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confidence: 99%

Substituted Pyrazolo[3,4‐d]pyrimidines: Microwave‐Assisted, Solvent‐Free Synthesis and Biological Evaluation

Oliveira‐Campos

Sivasubramanian

Rodrigues

et al. 2008

Helvetica Chimica Acta

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A simple and efficient method has been developed for the synthesis of various pyrazolo [3,4-d]pyrimidines by using microwave irradiation under solvent-free conditions. The advantages of applying microwave irradiation compared with the classical method were demonstrated. The structures of all the compounds were confirmed by the usual techniques and, in two cases, by X-ray analysis. The compounds did not display appreciable ability to inhibit xanthine oxidase activity. Screening for antifungal activity showed that some derivatives were active against four fungi, with more significant results for Botrytis.Introduction. -The development of simple and eco-friendly synthetic procedures constitutes an important goal in organic synthesis. Microwave-assisted organic synthesis (MAOS) is a fast-growing area of research, due to the generally short reaction times, and high purities and yields of the resulting products when compared to conventional methods [1].Microwave irradiation has been used to effect organic reactions such as pericyclic Solvent-free reactions under microwave irradiation are the subject of constant development because of its ease of set-up, mild conditions, and increased yields of products, cost efficiency, and environment friendliness compared to their solution counterparts [11].As part of our ongoing research program on heterocyclic compounds which may serve as leads for designing novel chemotherapeutic agents, we were particularly interested in pyrazolo-pyrimidines [12]. The pyrazole and pyrimidine derivatives have attracted the organic chemists interest due to their biological importance. Pyrazolopyrimidines and related fused heterocycles are known to exhibit several pharmacological activities such as CNS depressant [13]

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Acceleration of ortho ester Claisen rearrangement by a commercial microwave oven

Cited by 44 publications

References 4 publications

Organic Synthesis Using Microwaves in Homogeneous Media

Organic Synthesis Using Microwaves in Homogeneous Media

Synthesis of cyclic esters of N-toluenesulfonyl ?-aminophosphonic acid

Substituted Pyrazolo[3,4‐d]pyrimidines: Microwave‐Assisted, Solvent‐Free Synthesis and Biological Evaluation

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