Vinyl ether reactions

Five batches of the vinyl ether reaction were monitored by mid-lR using ReactlR MP (Mettler Toledo) during a pilot-plant campaign. Each batch yielded approximately 215 kg of vinyl ether for downstream production of aprepitant (Emend ) for phase 11 and 111 clinical trials. 

Oxidation of ethylene in alcohol with PdCl2 in the presence of a base gives acetal and vinyl ether. Reaction of terminal alkenes in alcohols affords regioisomers of the acetals 44 and 45 and vinyl ethers 46 depending on the structure of the alkenes. Internal alkenes 47 and alcohols give allylic ethers 48 and 50 and vinyl ethers 49 and 51 depending on which hydrogen is eliminated. 

Af-vinyl carbazole, reaction type 212 vinyl chloride, reaction type 212 vinyl ester, reaction type 212 vinyl ether, reaction type 212 vinyl fluoride, reaction type 212 vinylidene, reaction type 212 chloride At-vinylpyrrolidone, reaction type 212 virus, tobacco necrosis, crystal structure 166... 

Data acquisition in the neutral in analysis mode, where both quadmpole mass analyzers are operated in scanning mode but with a fixed m/z offset depending on the reaction performed, has been apphed to efficiently monitor these type of gas-phase reactions in complex mixtures of, e.g., phospholipids [52] and phosphonium ions in relation to chemical warfare agents [54]. The ethyl vinyl ether reaction with phospholipids yields a neutral gain of 26 Da for phosphatidylglycerols and of 57 Da for phosphatidylinositols [52], whereas the reaction of the phophonium ion with 1,4-dioxane yields a neutral gain of 44 Da [54]. 

As was the case for the smaller members of the series of vinyl ethers, atmospheric loss of propyl vinyl ether will occur on a relatively short timescale (< 1 h under most conditions), with reaction with OH, O3, and NO3 all playing a role. The reaction with NO3 is again of particular importance (lifetime 3 min. for highly polluted conditions, [NO3] = 3 X 10 molecule cm ). In keeping with the smaller vinyl ethers, reaction... 

They are colourless liquids with characteristic odours, and are prepared by the condensation of ketones with alkyl orthoformates in the presence of alcohols, or by the reaction of acetylenes with alcohols in presence of HgO and BF3. In some cases trichloroethanoic acid is used as the catalyst. They lose alcohol when heated and form vinyl ethers. Exchange of alcohol groups occurs when the ketals of the lower alcohols are boiled with alcohols of greater molecular weight. See acetals. 

Apparatus 250-ml round-bottomed flask for the cleavage of THF 500 ml flask (see Fig. 1) for the coupling with ethyl vinyl ether 1-1 flask (see Fig. 1) for the reaction with allenyl1ithiurn 500-ml round-bottomed flask for the deprotection. 

Hate 1. This excess was used to be absolutely sure that all a-chloroether would have reacted. Traces of this compound, if still present in the reaction mixture, will hydrolyse during the aqueous work up. The acid that is liberated can cause hydrolysis of the product to H2C=CH-C(=0)CH(CH3)0C2H5. HoLp. A. Prepared by introducing 0.30 mol of dry gaseous HCl (weight increase) into 45 ml of freshly distilled ethyl vinyl ether (excess) at -30°C. 

Oxidation of ethylene in alcohol with PdCl2 in the presence of a base gives an acetal and vinyl ether[106,107], The reaction of alkenes with alcohols mediated by PdCl2 affords acetals 64 as major products and vinyl ethers 65 as minor products. No deuterium incorporation was observed in the acetal formed from ethylene and MeOD, indicating that hydride shift takes place and the acetal is not formed by the addition of methanol to methyl vinyl etherjlOS], The reaction can be carried out catalytically using CuClj under oxygen[28]. 

In connection with mechanistic studies on the Wacker reaction, the transmetallation of ri-ethoxy- and /3-hydroxyethylmercury(II) chloride with PdCB has been carried out, giving ethyl vinyl ether and acetaldehyde[366]. The reaction proceeds by the formation of ri-ethoxy- and /3-hydroxyethylpalladium chlorides (401), which decompose as soon as they are formed. 

Butyl vinyl ether reacts with aroyl chlorides using Pd(OAc)2 without a ligand to give the unsaturated ketone 839, which is a precursor of a 1-aryl-1,3-dicarbonyl compound. The reaction is regioselective /3-attack. Addition of PhjP inhibits the reaction[718]. 

The cyclohexadiene derivative 130 was obtained by the co-cyclization of DMAD with strained alkenes such as norbornene catalyzed by 75[63], However, the linear 2 1 adduct 131 of an alkene and DMAD was obtained selectively using bis(maleic anhydride)(norbornene)palladium (124)[64] as a cat-alyst[65], A similar reaction of allyl alcohol with DMAD is catalyzed by the catalyst 123 to give the linear adducts 132 and 133[66], Reaction of a vinyl ether with DMAD gives the cyclopentene derivatives 134 and 135 as 2 I adducts, and a cyclooctadiene derivative, although the selectivity is not high[67]. 

In early work, vinyl chloride had been heated with stoichiometric amounts of alkaU alkoxides in excess alcohol as solvent, giving vinyl ethers as products (210). Supposedly this involved a Williamson ether synthesis, where alkaU alkoxide and organic haUde gave an ether and alkaU haUde. However, it was observed that small amounts of acetylene were formed by dehydrohalogenation of vinyl chloride, and that this acetylene was consumed as the reaction proceeded. Hence acetylene was substituted for vinyl chloride and only catalytic amounts of alkaU were used. Vinylation proceeded readily with high yields (211). 

Rea.ctlons, Vinyl ethers undergo all of the expected reactions of olefinic compounds plus a number of reactions that are both usehil and... 

Vinyl ethers and a,P unsaturated carbonyl compounds cyclize in a hetero-Diels-Alder reaction when heated together in an autoclave with small amounts of hydroquinone added to inhibit polymerisation. Acrolein gives 3,4-dihydro-2-methoxy-2JT-pyran (234,235), which can easily be hydrolysed to glutaraldehyde (236) or hydrogenated to 1,5-pentanediol (237). With 2-meth5lene-l,3-dicarbonyl compounds the reaction is nearly quantitative (238). 

The reaction of a vinyl ether with carbon dioxide and a secondary amine gives a carbamic ester (246). 

Acrolein as Diene. An industrially useful reaction in which acrolein participates as the diene is that with methyl vinyl ether. The product, methoxydihydropyran, is an intermediate in the synthesis of glutaraldehyde [111 -30-8]. 

Tetiafluoioethylene—peifluoiopiopyl vinyl ethei copolymeis [26655-00-5] aie made in aqueous (1,2) oi nonaqueous media (3). In aqueous copolymerizations water-soluble initiators and a perfluorinated emulsifying agent are used. Molecular weight and molecular weight distribution are controlled by a chain-transfer agent. Sometimes a second phase is added to the reaction medium to improve the distribution of the vinyl ether in the poljmier (11) a buffer is also added. 

Reactions between vinyl ethers or vinyl acetate and ethyleneimine have not been satisfactory (198), but ethyleneimine does add onto the double bond of /V,/V-dimethy1 vinyl amine to give 1-dimethyl amino-1-ethyleneiminoethane [5498-98-6] (217). 

Dioxetane decomposition has also been proposed to account for chemiluminescence from other reactions (43), including gas-phase reactions of singlet oxygen with ethylene and vinyl ethers (53). 

Endo adducts are usually favored by iateractions between the double bonds of the diene and the carbonyl groups of the dienophile. As was mentioned ia the section on alkylation, the reaction of pyrrole compounds and maleic anhydride results ia a substitution at the 2-position of the pyrrole ring (34,44). Thiophene [110-02-1] forms a cycloaddition adduct with maleic anhydride but only under severe pressures and around 100°C (45). Addition of electron-withdrawiag substituents about the double bond of maleic anhydride increases rates of cycloaddition. Both a-(carbomethoxy)maleic anhydride [69327-00-0] and a-(phenylsulfonyl) maleic anhydride [120789-76-6] react with 1,3-dienes, styrenes, and vinyl ethers much faster than tetracyanoethylene [670-54-2] (46). 

Alkoxyall l All l Peroxides. / /f-Butyl tetrahydropyran-2-yl peroxide [28627 6-5] (1), where R = tert — butyl, X = OR", R = H, R and R" = 1, 4 butanediyl, has been isolated. This is one of many examples of alkoxyalkyl alkyl peroxides which may be prepared by reaction of hydroperoxides with vinyl ethers (139) ... 

Vinyl chloride reacts with sulfides, thiols, alcohols, and oximes in basic media. Reaction with hydrated sodium sulfide [1313-82-2] in a mixture of dimethyl sulfoxide [67-68-5] (DMSO) and potassium hydroxide [1310-58-3], KOH, yields divinyl sulfide [627-51-0] and sulfur-containing heterocycles (27). Various vinyl sulfides can be obtained by reacting vinyl chloride with thiols in the presence of base (28). Vinyl ethers are produced in similar fashion, from the reaction of vinyl chloride with alcohols in the presence of a strong base (29,30). A variety of pyrroles and indoles have also been prepared by reacting vinyl chloride with different ketoximes or oximes in a mixture of DMSO and KOH (31). 

Alternatively, thermal cracking of acetals or metal-catalyzed transvinylation can be employed. Vinyl acetate or MVE can be employed for transvinylation and several references illustrate the preparation especially of higher vinyl ethers by such laboratory techniques. Special catalysts and conditions are required for the synthesis of the phenol vinyl ethers to avoid resinous condensation products (6,7). Direct reaction of ethylene with alcohols has also been investigated (8). 

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