Propenyl vinyl ether

Similar studies were performed for the radical polymers of cis-propenyl vinyl ether and 2-methylpropenyl vinyl ether, with the conclusion that the polymer structures were basically the same as that of poly (divinyl ether) (5 ). 

M. Sangermano, et al., Cationic photoinitiated copolymerization of 1-propenyl-vinyl ether systems. Eur. Polym. J. 2002, 38(4), 655-659. 

Z-Selective rearrangements are best carried out in dichloromethane. Use of other solvents (Table 5, entries 16-18) results in a decrease in the selectivity. An increase in the selectivity is achieved by lowering the reaction temperature. The 4-bromo substituent of the organoalu-minum reagent seems to be indispensible, since the rearrangement of l-methyl-2-propenyl vinyl ether using the less Lewis acidic bis(2,6-di-/m-butyl-4-methylphenoxy)methylaluminum furnishes 7-methyl-4-octenal in moderate yield (43%) and with an EjZ ratio of 19 81. 

Rearrangement of l-methyl-2-propenyl vinyl ether with bis(2,6-diphenylphenoxy)methyl-aluminum at — 20 °C results in the almost exclusive formation of the (E)-isomer [85% d.r. (E/Z) 97 3],... 

A solution of MesAl in hexane (1 M, 4.0 mmol) was added to a solution of 1-butyl-2-propenyl vinyl ether (2.0 mmol. Scheme 10) in 1,2-dichloroethane (15 ml) at 25 under an Ar atmosphere and the mixture was stirred for 15 min. Workup and TLC (Si02) purification gave the olefinic alcohol (0.28 g, 91% yield), the E/Z ratio being almost 1 1. 

Photoconductive polymers and copolymers were also synthesized by Haque et al. [249] from 2-(9-carbazolyl)-l-propenyl vinyl ether ... 

Poly(phenyl vinyl sulfide-alt-MA), 386 Polyphosphoric acid, dehydrating agent, 80, 84 Poly03-pinene-alt-MA), 352 Poly(propenyl chloride-alt-MA), 380 Poly(c -propenyIphenol-ait-MA), 375 Poly(4-propenylpyrocatechol-alt-MA), 375 Poly(propenylthiophene-co-MA), 387 Poly(cw-propenyl vinyl ether-co-MA), 326 Poly (/I-propyl endomethylene tetrahydrophthalate-co-MA), 289 Polypropylene, 461-464 MA copolymer blends, 292 MA ene adduct, 175 bismaleimide blends, 464 MA grafting procedures, 675... 

Propenylthiophene, MA copolymerization, 387 Propenyl vinyl ether, cis isomer, MA copolymerization, 326... 

Ethoxy-2-propyne, 1909 f Ethyl isopropyl ether, 2012 f Ethyl propenyl ether, 1956 f Ethyl vinyl ether, 1610... 

Azadienes of this sort were studied simultaneously by Mariano et al., who reacted mixtures of (1 ,3 ) and (1E, 3Z)-l-phenyl-2-aza-l,3-pentadiene 275 with several electron-rich alkenes, e.g., enamines and enol ethers (85JOC5678) (Scheme 61). They found the (l ,3 )-stereoisomer to be reactive in this process affording stereoselectively endo 276 or exo 277 piperidine cycloadducts in 5-39% yield, after reductive work-up with sodium borohydride. The stereochemistry of the resulting adducts is in agreement with an endo transition state in the case of dienophiles lacking a cis alkyl substituent at the /8-carbon (n-butyl vinyl ether, benzyl vinyl ether, and 1-morpholino cyclopentene), whereas an exo transition state was involved when dihydropyrane or c/s-propenyl benzyl ether were used. Finally, the authors reported that cyclohexene and dimethyl acetylenedi-carboxylate failed to react with these unactivated 2-azadienes. 

As the latter compounds are vinyl ethers, which are readily hydrolyzed under mildly acidic conditions, the base-acid sequence of reactions applied to an allyl ether brings about dealkylation. The acid hydrolysis in the second step can cause problems if other acid-labile protecting groups are present for example, l,2 5,6-di-0-isopropyli-dene-3-0-(l-propenyl)-a-D-glucofuranose gave204,205 1,2-O-isopropyli-dene-a-D-glucofuranose. 

The isomerization of allyl ethers to 1-propenyl ethers, which is usually performed with potassium tert-butoxide in dimethyl sulfoxide, can also be carried out under milder conditions using tris(triphen-ylphosphine)rhodium chloride,208 and by an ene reaction with diethyl azodicarboxylate,209,210 which affords a vinyl ether adduct. Removal of an O-allyl group may be achieved by oxidation with selenium dioxide in acetic acid,211 and by treatment with N-bromosuccinimide, followed by an aqueous base.201,212... 

Diels-Alder reaction, of acrolein with -butyl cyclohexenyl ether, n-butyl vinyl ether, and ethyl iso-propenyl ether, 34,30 of butadiene with maleic anhydride, 30,93... 

On addition the stereochemistry at the C=C bond of the vinyl ether remains constant. This was established by labeling studies and by the use of cis and trans ethyl propenyl ether. From the similarity of the activation parameters, the reaction characteristics, and the stereoselectivity of the cycloaddition step to those of the reactions of the same complexes with 1,3-dienes or ynamines an associative concerted nonsynchronous process was deduced.224... 

Enantiomer selection is also found in vinyl ether polymerization [226,227], The polymerization of cis- and trans- 1-methylpropyl propenyl ethers using (-)-menthoxyaluminum dichloride [227] and the copolymerization of rac- 1-methylpropyl vinyl ether with optically active monomers [226] are enantiomer selective. 

Special derivatives were reported by Dehennin and Scholler [364]. By reaction with acetone in the presence of TMCS, a hemiketal is produced, which dehydrates to the corresponding vinyl ether and the latter forms with HFB anhydride 1 -heptafluorobutanoyl-2-propenyl ether (Scheme 5.33). The reaction is carried out as follows. The steroid (2 10-3 mol) is dissolved in 0.1 ml of dry acetone and 0.1 ml of TMCS. Then HFB anhydride (0.05 ml) is added and the mixture is allowed to stand at room temperature for 1 h. The derivative is selective for sec.-hydroxyl groups and provides a higher ECD response that the HFB ester (up to 40 times higher for 5a-androstane-l 7(3-ol). 

Carbenium ions are sp2 hybridized with the empty orbital perpendicular to the plane containing the three substituents. Calculations confirm both the flat structure of carbenium ions and the shorter linkage with aryl substituents due to the partial double-bond character. As discussed previously, the positive charge is not localized just on the sp2-hybridized carbon of the carbenium ion, but is dispersed onto neighboring substituents. Table 1 presents the charge distribution in model carbenium ions formed by protonation of propene, isobutene, styrene, a-methylstyrene, methyl vinyl ether, and methyl propenyl ether. 

Propenyl Ethers and Unsaturated Cyclic Ethers Propenyl ethers (CH3—CH=CH—OR R = ethyl, isobutyl, etc. cis- and trans-isomers) and 3,4-dihydrofuran are linear and cyclic a,/3-unsaturated ethers, that can be regarded as / -substituted vinyl ether derivatives. For these monomers a few controlled/living cationic polymerizations have been reported. The HI/I2 system is generally effective for both linear and cyclic monomers [181,182,183], whereas a recent study by Nuyken indicates that the IBVE-HI adduct coupled with nBu4NC104 is suited for 3,4-dihydrofuran (see Section V.A.4) [184]. A variety of mono- and bifunctional propenyl ethers can readily be prepared by the ruthenium complex-catalyzed isomerization of corresponding allyl ethers [185]. 

There have been a number of unsuccessful attempts to trap 1,4-zwitterionic intermediates, - but there have also been some reported successes. At best, then, such trapping experiments are not uniformly diagnostic for zwitterionic intermediates. truns-Propenyl ethyl ether reacts with TONE in ethanol solvent at 25 C to give product (140). " The normal [2 + 2] adduct (139) gives this same product when allowed to react in ethanol, but at a slower rate. Just how fast this solvolysis might take place under the conditions of the cycloaddition reaction, with enol ether and TCNE present, is not clear. Acetone does not interfere with the addition of ethyl vinyl ether to TCNE, but the adduct (141) is converted over one week at room temperature to the six-membered ring product (142), which may be postulated as being derived from ci ture of a 1,4-zwitterionic intermediate in equilibrium with the cyclobutane structure. Alternatively, since acetone like ethanol is known to react with TCNE, it may be a case of acid-catalyzed solvent-assisted solvolysis. 

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