Concave Reagents, 21. Selective Acylations of Primary and Secondary Alcohols by Ketenes

Schyja, W.; Petersen, Sönke; Lüning, Ulrich

doi:10.1002/jlac.199619961223

Cited by 12 publications

(12 citation statements)

References 19 publications

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“…[1] Radial chromatography was carried out with chromatotron from Harrison Research Co. (silica gel layers with a thickness of 2 mm were used). (11): 1.13 g (50.0 mmol) of sodium was dissolved in 200 ml of dry ethanol and 10.0 g (43.6 mmol) of dimethyl 4-chloro-2,6-pyridinedicarboxylate (10) [12] was added in portions.…”

Section: Methodsmentioning

confidence: 99%

“…Ϫ The reaction conditions were chosen as in ref. [1] . A mixture of EtOH, iPrOH and tBuOH was used, the tert-butyl ester was not detected.…”

Section: Selectivity Measurementsmentioning

confidence: 95%

“…Ϫ [g] Reaction conditions were chosen as in ref. [1] . Ϫ [h] An HPLC column was packed with the insoluble polymer [f] , and the reaction mixture was slowly pressed through the column.…”

Section: Selectivity Measurementsmentioning

confidence: 95%

“…1998, 1077Ϫ1084 1078 of the chloropyridine derivative 10. Total reduction to the bisalcohol 11 and selective oxidation with SeO 2 afforded the dialdehyde 12 which was cyclized with a diamine 13 or 14 [1] dendrimer A…”

Section: Selectivity Measurementsmentioning

confidence: 99%

“…[1] These selectivities have been found for intermolecular (EtOH/iPrOH) and intramolecular competition (1,2-propanediol, 3). [1] In the present work we have extended the acylation reaction to 1,3-butanediol (5) and to the glucose derivative 7. In 7, the two OH groups to be differentiated are extremely similar, they are both secondary and equatorial!…”

mentioning

confidence: 91%

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Concave Pyridines for Selective Acylations of Polyols

Lüning¹,

Petersen

Schyja

et al. 1998

Eur. J. Org. Chem.

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Section: Methodsmentioning

confidence: 99%

“…Ϫ The reaction conditions were chosen as in ref. [1] . A mixture of EtOH, iPrOH and tBuOH was used, the tert-butyl ester was not detected.…”

Section: Selectivity Measurementsmentioning

confidence: 95%

“…Ϫ [g] Reaction conditions were chosen as in ref. [1] . Ϫ [h] An HPLC column was packed with the insoluble polymer [f] , and the reaction mixture was slowly pressed through the column.…”

Section: Selectivity Measurementsmentioning

confidence: 95%

Section: Selectivity Measurementsmentioning

confidence: 99%

mentioning

confidence: 91%

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Concave Pyridines for Selective Acylations of Polyols

Lüning¹,

Petersen

Schyja

et al. 1998

Eur. J. Org. Chem.

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Concave reagents. 31. A Merrifield bound concave pyridine for the selective acylation of polyols

Lüning¹,

Hacker

1999

J. prakt. Chem.

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The enhancement of selectivity is a major goal in the development of new reagents and catalysts, and continuously new answers are found for questions of chemo-, regio-, diastereoand enantioselectivity. But in many cases, the price for increased selectivities is a costly synthesis of the reagent or catalyst.While catalysts leave a reaction sequence unaltered reagents are consumed. However, many reagents can also be used over and over again, if a method has been established which "recharges" the reagent. For example a protonation or deprotonation can reestablish an acid or a base, respectively, or redox-active reagents can be "recharged" after the reaction by the use of an appropriate oxidizing or reducing process. Therefore, the following considerations are valid for both classes, for catalysts and for reagents which can be regenerated, although only one of the classes may be mentioned.A multistep synthesis of a new catalyst (or reagent) will only pay off if it can be recovered and purified easily. These requirements are fulfilled by polymer bound catalysts.Since the pioneering work of Merrifield [1], polymeric resins play an important role in organic synthesis [2]. Their use as a platform for the synthesis of larger molecules has enabled the chemist to construct automatic machines for the synthesis of oligopeptides or oligonucleotides [3]. In these reactions, the growing oligomer is covalently bound to the polymer, and the reactions are carried out by alternating turns of dipping the resin into the reagent solutions and washing. The same principle is used in combinatorial chemistry which uses several different reagents in parallel reactions to generate libraries of oligomers [4]. In the final reaction step of these reactions, the products must be cleaved off the polymer.A second use of polymers in organic chemistry exchanges the positions of substrate and reagent: the reagent is bound to a polymer, the substrate is dissolved. After the reaction, product and reagent can again be easily separated by filtration, with the reagent remaining on the polymer. If the reagent is a catalyst or can easily be regenerated it can thus be used over Abstract. The concave pyridine 2a has been synthesized in 61% yield in the two macrocyclization steps. After deprotection to give 2b, the concave pyridine has been attached to a Merrifield resin, and the resulting polymer 10 containing 0.3 mmol 2/g has been used as a selective acylation catalyst for the addition of propane-1,2-diol (11) and the glucose derivative 14a to diphenylketene (12) to form selectively 2-hyand over again, and the synthetic effort in synthesizing the catalyst or reagent pays off. Therefore, many reagents and catalysts have been attached to polymers [5]. In addition with polymer bound catalysts, continuous flow set-ups can easily be realized, which will be shown here for a concave reagent.Concave reagents [6] possess a lamp-shade like geometry with a reactive group (light bulb) on the inside of the molecule. As with enzymes where the high selectivity is largely c...

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How To Synthesize Macrocycles Efficiently by Using Virtual Combinatorial Libraries

Storm¹,

Lüning²

2002

Chem. Eur. J.

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Concave Reagents, 21. Selective Acylations of Primary and Secondary Alcohols by Ketenes

Cited by 12 publications

References 19 publications

Concave Pyridines for Selective Acylations of Polyols

Concave Pyridines for Selective Acylations of Polyols

Concave reagents. 31. A Merrifield bound concave pyridine for the selective acylation of polyols

How To Synthesize Macrocycles Efficiently by Using Virtual Combinatorial Libraries

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