Ethere preparation

A), -Dinitrohenzoates. Only suitable for symmetrical aliphatic ethers. Preparation, see above. The yields are usually very low. 

The lithiation of allene can also be carried out with ethyllithium or butyl-lithium in diethyl ether (prepared from the alkyl bromides), using THF as a cosolvent. The salt suspension which is initially present when the solution of alkyllithium is cooled to -50°C or lower has disappeared almost completely when the reaction between allene and alkyllithium is finished. 

In some experiments the presence of hexane is undesirable in view of the volatility of the products. In these cases one can use butyllithium in pentane (prepared from butyllithium in hexane, by replacing the hexane with pentane see Exp. 10) or ethyllithium in diethyl ether, prepared from ethyl bromide and 11thiurn (see Exp. 1). 

The alkylations proceeded much more slowly, when ethyl- or butyllithium in diethyl ether, prepared from the alkyl bromides, had been used for the metallation of allene, in spite of the presence of THF and HMPT as co-solvents. 

Note 1. Butyl- or ethyllithium in diethyl ether, prepared from the alkyl bromide, contains LiBr, which may react with chlorine to form bromine, so that RCeC-Br will also be formed. 

To a refluxing solution 0. phenylmagnesium bromide in 650 ml of diethyl ether, prepared from 1.15 mol of broraobenzene (see Chapter 11, Exp. 5) was added 1.00 mol of ally] bromide at a rate such that refluxing was maintained (about 30 min). 

A solution of methylmagnesium bromide in 150 ml of diethyl ether, prepared from 0.5 mol of methyl bromide (see Chapter II, Exp. 5) was subsequently added in 20 min with cooling at about 20°C. After the addition the mixture was warmed for 2 h under reflux (the thermometer and gas outlet were replaced with a reflux condenser), a black slurry being formed on the bottom of the flask. The mixture was cooled in a bath of dry-ice and acetone and a solution of 30 g of ammonium chlori.de in 200 ml of water was added with vigorous stirring. The organic layer and four ethereal extracts were combined, dried over potassium carbonate and subsequently concentrated in a water-pump vacuum. Careful distillation of the residue through a 40-cm... 

To a mixture of 0.10 mol of 1-ethoxy-l,2-heptadiene (see this chapter, Exp. 13) and 120 ml of diethyl ether was added 1 g of copper(I) bromide. A solution of butyl magnesium bromide in about 200 ml of diethyl ether, prepared from 0.25 mol of butyl bromide (see Chapter II, Exp. 5) was added in 15 min. The reaction was weakly exothermic and the temperature rose slowly to about 32°C. The mixture was held for an additional 40 min at that temperature, then the black reaction mixture was... 

Hydroxyethyl- andHydroxypropylcelluloses. HydroxyalkylceUuloses are ceUulose ethers prepared by reaction of alkaU ceUulose with ethylene oxide, to prepare hydroxyethjlceUulose (HEC) [9004-62-0] or propylene oxide, to prepare hydroxypropylceUulose (HPC) [9004-64-2]. 

The p-cyanobenzyl ether, prepared from an alcohol and the benzyl bromide in the presence of sodium, hydride (74% yield), can be cleaved by electrolytic reduction (—2.1 V, 71% yield). It is stable to electrolytic removal ( — 1.4 V) of a tritylone ether [i.e., 9-(9-phenyl-10-oxo)anthiyl ether]. ... 

The tetrahydropyranyl ether, prepared from a phenol and dihydropyran (HCl/ EtOAc, 25°, 24 h), is cleaved by aqueous oxalic acid (MeOH, 50-90°, 1-2 h). ... 

Zn, HOAc, 25°, 1 h, 88-96% yield. Phenacyi andp-bromophenacyl ethers of phenols are stable to 1 % ethanolic alkali (reflux, 2 h), and to 5 N sulfuric acid in ethanol-water. The phenacyi ether, prepared from /3-naphthol, is cleaved in 82% yield by 5% ethanolic alkali (reflux, 2 h). 

A solution of diazomethane in 2.4 liters ether, prepared from 177 g (1.71 moles) of A-nitrosomethylurea and 530 ml of 40% aqueous potassium hydroxide, is added to 26.4 g (0.81 moles) 17 -acetoxyandrosta-1,4,6-triene-3-one in 250 ml ether. After 6 days at room temperature the ether is removed by distillation at reduced pressure and the residue is chromatographed on 1.5 kg of silica gel (deactivated with water 10% v/w). The product is eluted with methylene dichloride and recrystallized from diisopropyl ether-methylene dichloride to give 11 g (37 %) 17 -acetoxyandrosta-4,6-dien-3-one-[2a,la-c]-A -pyrazoline mp 161° (dec.) —91° (CHCI3) ... 

The tetrahydropyranyl ether, prepared from a phenol and dihydropyran (HCl/EtOAc, 25°, 24 h) is cleaved by aqueous oxalic acid (MeOH, 50-90°, 1-2 h). Tonsil, Mexican Bentonite earth, HSZ Zeolite, and H3[PW,204o] have also been used for the tetrahydropyranylation of phenols. The use of [Ru(ACN)3(triphos)](OTf)2 in acetone selectively removes the THP group from a phenol in the presence of an alkyl THP group. Ketals of acetophenones are also cleaved. ... 

The vinyl ether prepared above (4.5 g) is dissolved in 30 ml of ether and mixed with 60 ml of 1 A sulfuric acid in a 250-ml flask equipped with a magnetic stirrer and a condenser. The mixture is gently refluxed with stirring for 2.5 hours, and the cooled... 

To a solution of 5 mmol of 1,3-diphcnyl 3-[(S )-2-mcthoxymethyl-l-pyrrolidinyl]-2-propenyl[lithium in 10 mL of tort-butyl methyl ether (prepared according to Section D. 1.1.1.2.2.3.) at 0°C. 6.25 mmol of the aldehyde (and eventually 6.25 mmol of lithium halogenide in 27 mL of leri-butyl methyl ether) are added dropwise. Stirring is continued for 2 h and 0.39 g (5.0 mmol) of acetyl chloride are added. After 2 h stirring at r.t., 10 mL of the solvent, 50 mL of diethyl ether and 10 mL of 2 N aq hydrochloric acid are added and stirring is continued for 2 h at 20 C. The organic layer is extracted with three 20 mL-portions of water and the aqueous solutions are reextracted with diethyl ether. The combined aqueous solutions are dried over Na,S04, concentrated in vacuum and the residue distilled to yield a mixture of xyn- and on/i-ketones >90% ee, determined by H-NMR with Pr(hfc)3. 

Some representative Claisen rearrangements are shown in Scheme 6.14. Entry 1 illustrates the application of the Claisen rearrangement in the introduction of a substituent at the junction of two six-membered rings. Introduction of a substituent at this type of position is frequently necessary in the synthesis of steroids and terpenes. In Entry 2, formation and rearrangement of a 2-propenyl ether leads to formation of a methyl ketone. Entry 3 illustrates the use of 3-methoxyisoprene to form the allylic ether. The rearrangement of this type of ether leads to introduction of isoprene structural units into the reaction product. Entry 4 involves an allylic ether prepared by O-alkylation of a (3-keto enolate. Entry 5 was used in the course of synthesis of a diterpene lactone. Entry 6 is a case in which PdCl2 catalyzes both the formation and rearrangement of the reactant. 

A sample of the peroxide in ether, prepared according to a published procedure [1], was being evaporated to dryness with a stream of air when it exploded violently. Handling the peroxide as a dilute solution at low temperature is recommended [2], See other diacyl peroxides... 

Perfluorotributylamine, as blood substitute, 4 112-113 Perfluorovinyl ethers, preparation of, 18 329-330... 

Table 9.21 gives the yields, times to maximum yield, retention times and least detectable amounts of the herbicide esters or ethers prepared using the above method. In no instance was the standard error of the mean yield >2%. The least detectable amount is based on a peak giving a response of twice the background signal. 

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