Ethers bis

The aqueous layer was extracted with diethyl ether. The combined ethereal solutions were dried over potassium carbonate, after which the greater part of the diethyl ether was distilled off at normal pressure through a 40-cm Vigreux column (bath temperature < 90°C). Careful distillation of the remaining liquid afforded the bis-ether, b.p. 47-49°C/18 mmHg, Op 1.4469, in 78% yield. 

To a solution of 22 g of K0-tert.-Ci,H9 (see Exp. 4, note 2) in 400 ml of anhydrous liquid ammonia were added 22 g of the bis-ether (note 1). After stirring for 4 h, 20 g of powdered ammonium chloride were introduced in small portions. The ammonia was removed by placing the flask in a water-bath at 40°C, then 200 ml of water were added and five extractions with small portions of redistilled pentane were carried out. The combined extracts were washed with water, dried over magnesium sulfate and then concentrated in a water-pump vacuum. The residue was carefully distilled through a 40-cm Vigreux column, giving the allenic bis-ether,... 

Cumulenic ethers with the 4-positions blocked by alkyl groups can be obtained from bis-ethers, R0-CH2C=C-C(R )(r2)0R, and sodium amide in liquid NHj, applying the... 

Note i. If only one equivalent of ethyl 1ithium is used, the conversion of the bis--ether is not complete. The necessity for two equivalents can be explained by assumin g that the rates of 1,4-elimination of ethanol and subsequent 1-lithiation are comparable. 

To a mixture of 0.15 mol of the acetylenic bis-ether (see Chapter VIII-6, Exp.l) and 100 ml of dry diethyl ether was added in 20 min with cooling between -40 and -50°C 3 solution of 0.30 mol of ethyllithium (note 1) in about 250 ml of diethyl ether (see Chapter II, Exp. 1). After stirring for an additional 15 min at -45°C the mixture was cautiously poured into 200 ml of ice-water and 50 g of crushed ice (note 2). After vigorous shaking the layers were separated and the aqueous layer was extracted twice with small portions of diethyl ether. The combined ethereal solutions were dried over magnesium sulfate. After concentration of the... 

Note 4. Gas-liquid chromatography showed complete conversion into the bis-ether. 

Unlike common commercial dianhydrides such as PMDA and BTDA, bis(ether anhydride)s possess moderate reactivity toward nucleophiles because of the electron-donating property of the ether groups. Bis(ether anhydtide)s are hardly affected by atmospheric moisture. The stabiUty and generally better solubiUty of bis(ether anhydtide)s provide significant advantages in manufacturing operations. 

This scheme eliminates the process of converting bis(etherimide)s to bis(ether anhydride)s. When polyetherimides are fusible the polymerization is performed in the melt, allowing the monamine to distill off. It is advantageous if the amino groups of diamines are more basic or nucleophilic than the by-product monoamine. Bisimides derived from heteroaromatic amines such as 2-arninopyridine are readily exchanged by common aromatic diamines (68,69). High molecular weight polyetherimides have been synthesized from various N,lSf -bis(heteroaryl)bis(etherimide)s. 

Fig. 3.3 H NMR and X-ray crystallography study of the bis-ether complex 28. [Denmark, S.E. Edwards, ).P. Wilson, S.R.J. Am. Chem. Soc. 1992, 114, 2592. Reprinted with permission from The American Chemical Society]...

BENZENE, 1,1 -[(ethylenoxyl)methylcne] bis- [Ether, diphenylmethyl vinyl],... 

In rare cases, the Pd-catalyzed intramolecular allylic etherification has been extended to the construction of medium-sized rings. Both an 11-membered bis-ether ring (Equation (34))164 and an eight-membered ether ring (Equations (35) and (36))155 have been prepared in this fashion. In the latter case, the choice of ligand dictated the regiochemical outcome. 

A series of 1-difluoroaminoalkanols prepared from difluoramine and an aldehyde or ketone, together with their acetates or bis(ethers), were all shock- and friction-sensitive explosives. 

Since the acetoxy and methoxy synthetic derivatives exhibited herbicidal activity, we were curious whether this also occurred with other esters and ether derivatives of 1 and its isomer, 3,7-dimethyl-6-hydroxy-8-methoxyisochroman (4). We reasoned that 3,7-dimethyl-6,8-dimethoxyisochroman (3) represents a logical precursor for the systematic preparation of the desired ester and ether analogs of isochromans 1 and 4. To test this conjecture, we needed both an efficient synthesis of bis-ether 3 and a practical way to demethylate the C(6) or C(8) ethers selectively. 

Dioxane behaves as an acetal, 1,4-dioxane as a bis-ether, and 2,5-dioxopiperazine (538) as a bis-lactam. 

Etherification of isohexides with substituted-benzyl chloride in aqueous sodium hydroxide, or by means of sodium hydride in dimethyl sulfoxide, yields mixtures of mono- and bis-ethers, which can be conventionally separated by distillation or by column chromatography.176 The preparation of some phenyl ethers was also described, using the tosylate-phenoxide exchange reaction. Monoethers (88) synthesized in this way were transformed into carbamates (89) by reaction with sodium cyanide-trifluoroacetic acid (see Scheme 18). 

Satake et al. have described the mechanistic aspects of the formation of 2-methoxy-277-azepine derivatives lla-d from 377-azepines lOa-d upon reaction with bromine <2003H(60)2211> (Scheme 1). Unlike the situation observed with cycloheptatrienes, delocalized azatropylium salts were not formed from the reaction of 377-azepines with bromine in the absence of an alcoholic solvent. Reaction of 12 with bromine gave 13 plus the bis-ether 14 and bromomethane. The product 14 was also observed in the reaction of 12 with NBS (0.5 equiv) with 1 equiv of 7V-bromosuccinimide (NBS) 12 afforded the succinimido-substituted derivative 15, which upon elimination of HBr in the presence of base gave the 277-azepine 16 (Scheme 2) <2003H(60)2211>. 

Selective epoxidation of the isolated double bond (Equation 35) in the ester 79, prepared from citronellal and triphenyl(ethoxycarbonylmethylene)phosphorane, followed by treatment with Na2PdCl4 and v/-butyl hydroperoxide gives the bis-ether 80 <1994CC903>. 

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