From halo ethers

Vinyl ethers have also been prepared by addition of alkoxides to acetylene,6 7 6 elimination from halo ethers and related precursors,6 8 and vinyl exchange reactions.6 Reaction of an electrophilic tungsten carbenoid with methylene phosphorane or diazomethane also produces vinyl ethers.9 Enol ethers have resulted from the reaction of some tantalum and niobium carbenoids with esters,10 and the reaction of phosphoranes with electrophilic esters.4... 

Two techniques are commonly used in the preparation of olefinic ethers from halo ethers. The first involves heating a /5-halo ether with fused or powdered potassium hydroxide. This method is typified by the conversion of -phenoxyethyl bromide to phenyl vinyl ether (69%) and, /5 -dichlorodiethyl ether to divinyl ether (61%). In the latter case, yields are improved in the presence of ammonia gas. In the second procedure, an aliphatic or aromatic chloro ether is heated with pyridine to 115°. This method is of value in the preparation of several methoxystyrenes. Chloroalkylation of the aromatic ether is followed by dehydrohalogenation. 

This method of reaction is also applicable to the preparation of hydroxy nitriles (from chlorohydrins, yields about 80%)452 and a-alkoxy nitriles (from -halo ethers and copper cyanide, yields 55-80%).453... 

The elimination of OR and halogen from P-halo ethers is called the Boord reaction. It can be carried out with zinc, magnesium, sodium, or certain other reagents.The... 

See Ref. 150, p. 136, for reagents that produce alkenes from p-halo ethers and esters, and from halohydrins. 

For 1,2-disubstituted epoxides, the regiochemical outcome of nucleophilic attack becomes less predictable. However, in the case of epoxy ethers chelation control can be used to deliver the nucleophile preferentially to the epoxide carbon away from the ether moiety. Thus, treatment of epoxy ether 61 with an imido(halo)metal complex, such as [Cr(N-t-Bu)Cl3(dme)], leads to the clean and high-yielding production of the chlorohydrin 64. The regioselectivity is rationalized in terms of initial formation of a chelated species (62), followed by attack at C-3 to form the more stable 5-membered metallacyclic alkoxide 63 <00SL677>. 

The mechanism of this reaction has been investigated in some detail. RX must be an activated halide, such as a benzyl halide, a-halo ether, or a 1,1-dihalocarbon where at least one of the halides is Br or L Simple halocarbons do not react, nor does methylene chloride. Reaction with chloroform is slow, while reaction with carbon tetrachloride is instantaneous at room temperature. The (pseudo) first-order rate constant is linearly correlated to the polarographic reduction potential of the halide thus electron transfer from (38) to RX (equation 57) is the rate-determining step, followed by rapid cleavage of the RX radical anion into R and X . 

The method has been used for the preparation of dihalides, e.g., 1,9-dichlorononane (93%) unsaturated halides, e.g., 11-undecylenyl chloride (83%) halo ethers, e.g., /3-ethoxyethyl chloride (80%) halo ketones, e.g., desyl chloride (79%) halo esters, e.g, methyl a-chloropropionate (71%) halo cyanides, e.g., phenylchloroacetonitrile (80%) and aminoalkyl halides,An interesting isomerisation has been observed in liberating 2-diethylamino-l-chloropropane from its hydrochloride salt l-diethylamino-2-chloropropane is formed. ... 

Olefinic amino aciefe and alkoxy amino acids are obtained by this method from olefinic halides and halo ethers, respectively. 

The reduction of diazonium salts by sodium sulfite forms monosub-stituted arylhydrazines. An improved procedure for the synthesis of phenylhydrazine in 84% yield is typical. Arylhydrazine salts substituted in the nucleus with halo," ether, carboxyl, or nitro groups have been prepared. The free bases are liberated from the salts by the action of aqueous sodium hydroxide or sodium acetate. 

The action of zinc and alcohol on dibromo acetals, CHBtjCH(OR)2, gives olefinic halo ethers, BrCH CHOR (50-78%). A similar elimination from a-halo ortho esters by means of sodium sand in boiling benzene leads to ketene acetals. 

Treatment of a-halo ethers with metallic cyanides such as cuprous, mercuric, or silver cyanides gives the corresponding cyano ethers the alkali cyanides are without effect. Very little of the corresponding isonitriles are encountered despite the fact that these compounds often result from the interaction of heavy-metal cyanides and alkyl halides. Generally, cuprous cyanide, the most commonly used reagent, is suspended in dry anhydrous ether or dry benzene and treated with the halo ether under gentle reflux (55-80%). 

The a-position of an ether is susceptible to attack by free radicals and, in certain circumstances, by halogens. Ethers are slowly oxidized by the oxygen from air to form peroxides- This can be a hazard in stored bottles of ethers, particularly with the higher ethers such as di-isopropyl ether. These peroxides may be destroyed by treatment with iron(IT) sulfate. Chlorine reacts with ethers, particularly in sunlight. These a-halo ethers then decompose to the aldehyde and an alcohol. 

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