Über Mono‐ und Dioxymethylen‐dimethyläther

Abstract

L o b e r i n g , F 1 e i s c hm a n n :[Jahrg. 70 wcrte seiner freien Saure, des Methylesters uiid des p-Bromphenacyl-Derivates beweiseu, iibersieht aber, daB die Unterscheidung zwischen den moglichen Homologen auf diesem Wege nicht mehr leicht moglich ist. Nicht vie1 besser steht es mit seiner Methoxylbestimmung, die allerdings riicht veroffentlicht wurde, umso rnehr, als mail iiber die Reinheit des Methylesters nicht inforniiert wird.Eine vollig sichere Unterscheidung ist am besten durch Titration xu erbringen. Wir wissen, daf3 bei soIcheii hohermolekutaren Sauren die Mikrotitration nur bei Anwendung besonderer Vorsichtsmal3regeli verliWliche Wertc gibt. Deshalb haben wir eine Menge iri der GroBenordnung von I g der sorgfiiltig gereinigten Saure unter liedingungen titriert, die eine besonders enge E'ehlerbreite gewahrleisten. Nach unseren Versuchen ist an dem Vorliegen der C,,-Saure nicht mehr ZLI zweifeln.Zwecks Abkiirzung weiterer polemischer Auseinandersetzungen sclilageri wir vor, daB Hr. Raudnitz zur Klarstellung der Angelegenheit gemeinsam mit UIIS die Untersuchung der strittigen Siure im 11. Chem. Univ.-Laborat. in Wieri vornimmt. I'alls dies nicht moglich ist, werden wir eineii neutralen E'orscher einladen, die I'ormel der Abbausaure des Hexahydro-ammoresinols zu iiberpriifen.

NHC-CDI Betaine Adducts and Their Cationic Derivatives as Catalyst Precursors for Dichloromethane Valorization

“… 24 Yet, it has been known for a very old time that neat dichloromethane does not react with sodium methoxide, or it does only reluctantly under forcing conditions to afford complex mixtures of products. 25 We performed a series of tests with different amounts of solid sodium methoxide suspended in neat DCM at 25 and 60 °C, using a sealed ampule with a magnetic stirrer as a reactor. We confirmed that, whereas hardly any detectable quantity of methylal was formed in the absence of 2a , the addition of a catalytic amount of the latter (from 2 to 0.2 mol %) led to the quantitative conversion of NaOMe into methylal and NaCl.…”

“…4 h. As shown in Table 2 , no methylal was formed in the absence of any PTC reagent, confirming the inertness of DCM against solid NaOMe reported in old literature sources cited above. 25 Nevertheless, when we added the same catalyst loading of NBu 4 Cl, 18-crown-6, 15-crown-5, or the imidazolium salt ICy·HBF 4 (the precursor of the NHC carbene ICy, one of the constitutive parts of 1a ), DCM conversion was observed, albeit with significant differences. Remarkably, 2a proved the most active of the set.…”

“…Methylal or dimethoxymethane is an interesting target since it can be used as a green solvent (far less toxic than DCM itself) or as a safer surrogate of formaldehyde, preventing the use of this toxic substance or its insoluble polymer, paraformaldehyde . Yet, it has been known for a very old time that neat dichloromethane does not react with sodium methoxide, or it does only reluctantly under forcing conditions to afford complex mixtures of products . We performed a series of tests with different amounts of solid sodium methoxide suspended in neat DCM at 25 and 60 °C, using a sealed ampule with a magnetic stirrer as a reactor.…”

“…The only difference with the preparative conditions was that, in order to facilitate data collection, this set of experiments was performed at a slightly lower temperature, 40 °C, at which the half-conversion time would be ca. 4 h. As shown in Table , no methylal was formed in the absence of any PTC reagent, confirming the inertness of DCM against solid NaOMe reported in old literature sources cited above . Nevertheless, when we added the same catalyst loading of NBu 4 Cl, 18-crown-6, 15-crown-5, or the imidazolium salt ICy·HBF 4 (the precursor of the NHC carbene ICy, one of the constitutive parts of 1a ), DCM conversion was observed, albeit with significant differences.…”

Synthesis of the Adrenergic Bronchodilators (R)-Terbutaline and (R)-Salbutamol from (R)-Cyanohydrins1

“…3-(Methoxymethoxy)-4-methylbenzaldehyde (3b). Potassium carbonate (5.0 g, 36 mmol) was suspended in a solution of 1b (4.9 g, 36 mmol) in acetonitrile (50 mL), and chloromethyl methyl ether 31 (5 mL of a 65% ic solution) was added dropwise. After stirring for 18 h, the solid was filtered off and washed with acetonitrile.…”