Ethers, vinyl from esters

Kobayashi et al. found that lanthanide triflates were excellent catalysts for activation of C-N double bonds —activation by other Lewis acids required more than stoichiometric amounts of the acids. Examples were aza Diels-Alder reactions, the Man-nich-type reaction of A-(a-aminoalkyl)benzotriazoles with silyl enol ethers, the 1,3-dipolar cycloaddition of nitrones to alkenes, the 1,2-cycloaddition of diazoesters to imines, and the nucleophilic addition reactions to imines [24], These reactions are efficiently catalyzed by Yb(OTf)3. The arylimines reacted with Danishefsky s diene to give the dihydropyridones (Eq. 14) [25,26], The arylimines acted as the azadienes when reacted with cyclopentadiene, vinyl ethers or vinyl thioethers, providing the tet-rahydroquinolines (Eq. 15). Silyl enol ethers derived from esters, ketones, and thio-esters reacted with N-(a-aminoalkyl)benzotriazoles to give the /5-amino carbonyl compounds (Eq. 16) [27]. The diastereoselectivity was independent of the geometry of the silyl enol ethers, and favored the anti products. Nitrones, prepared in situ from aldehydes and N-substituted hydroxylamines, added to alkenes to afford isoxazoli-dines (Eq. 17) [28]. Addition of diazoesters to imines afforded CK-aziridines as the major products (Eq. 18) [29]. In all the reactions the imines could be generated in situ and the three-component coupling reactions proceeded smoothly in one pot. 

Substitution at the Carbon—Chlorine Bond. Vinyl chloride is generally considered inert to nucleophilic replacement compared to other alkyl halides. However, the chlorine atom can be exchanged under nucleophilic conditions in the presence of palladium [7440-05-3] Pd, and certain other metal chlorides and salts. Vinyl alcoholates, esters, and ethers can be readily produced from these reactions. 

In aldol reactions, especially Mukaiyama aldol reactions, TiIV compounds are widely employed as efficient promoters. The reactions of aldehydes or ketones with reactive enolates, such as silyl enol ethers derived from ketones, proceed smoothly to afford /3-hydroxycarbonyl compounds in the presence of a stoichiometric amount of TiCl4 (Scheme 17).6, 66 Many examples have been reported in addition to silyl enol ethers derived from ketones, ketene silyl acetals derived from ester derivatives and vinyl ethers can also serve as enolate components.67-69... 

However, most asymmetric 1,3-dipolar cycloaddition reactions of nitrile oxides with alkenes are carried out without Lewis acids as catalysts using either chiral alkenes or chiral auxiliary compounds (with achiral alkenes). Diverse chiral alkenes are in use, such as camphor-derived chiral N-acryloylhydrazide (195), C2-symmetric l,3-diacryloyl-2,2-dimethyl-4,5-diphenylimidazolidine, chiral 3-acryloyl-2,2-dimethyl-4-phenyloxazolidine (196, 197), sugar-based ethenyl ethers (198), acrylic esters (199, 200), C-bonded vinyl-substituted sugar (201), chirally modified vinylboronic ester derived from D-( + )-mannitol (202), (l/ )-menthyl vinyl ether (203), chiral derivatives of vinylacetic acid (204), ( )-l-ethoxy-3-fluoroalkyl-3-hydroxy-4-(4-methylphenylsulfinyl)but-1 -enes (205), enantiopure Y-oxygenated-a,P-unsaturated phenyl sulfones (206), chiral (a-oxyallyl)silanes (207), and (S )-but-3-ene-1,2-diol derivatives (208). As a chiral auxiliary, diisopropyl (i ,i )-tartrate (209, 210) has been very popular. 

Krespan also found that allyl alcohol added to 1-mcthoxy-2-(trifluoromethyl)tetrafluoro-propcnc, derived from perfluoro(2-mclhylpropene). to give the rearranged ester 5. a presage of the Johnson Claiscn rearrangement. Reactions of allylic alcohols with vinyl ethers derived from perfluoro(2-methylpropene) were subsequently studied by Andreev and co-workers11 and are discussed below. 

The products of solvolysis in aqueous solvents are generally ketones (119) presumably deriving from the corresponding enols (120). Vinyl ethers (121) and esters (122) are obtained in non-aqueous solvents or in... 

R)-(-)-2,2-Diphenylcyclopentanol (1) is a highly effective chiral auxiliary in asymmetric synthesis. Hydrogenation of chiral 0-acetamidocrotonates derived from this alcohol has afforded the corresponding 0-amido esters with high diastereoselectivity (96% de).6 In addition, (R)-1 has been used as a chiral auxiliary in Mn(lll)-based oxidative free-radical cyclizations to provide diastereomerically enriched cycloalkanones (60% de).7 Our interest in (R)-(-)-2,2-diphenylcyclopentanol is its utility as a chiral auxiliary in Lewis acid-promoted, asymmetric nitroalkene [4+2] cycloadditions. The 2-(acetoxy)vinyl ether derived from alcohol (R)-1 is useful for the asymmetric synthesis of 3-hydroxy-4-substituted pyrrolidines from nitroalkenes (96% ee).8 In a similar fashion, a number of enantiomerically enriched (71-97% ee) N-protected, 3-substituted pyrrolidines have been prepared in two steps from 2-substituted 1-nitroalkenes and (R)-2,2-diphenyl-1-ethenoxycyclopentane (2) (see Table).9... 

Recently, Claisen rearrangement of allyl-vinyl ether prepared from glycal ester with Tebbe reagent was reported [91]. In contrast to the Ireland-Claisen rearrangement, in principle, a non-enolizable ester can be employed (O Scheme 63). This method was applied for the synthesis of C-disaccharide. 

The vinyl group can also be transferred to alcohols to form vinyl ethers starting from vinyl chloride [66], vinyl esters [76], and vinyl ethers [77]. The transfer to water corresponds to a hydrolysis which readily takes place with all vinylic compounds in the presence of palladium salts to form acetaldehyde [78]. 

As can be seen from equations 2-5, the formation of A -acylenamines proceeds from derivatives of carboxylic acids (having an oxidation level equal to three ), namely anhydrides or add halides RCOX or amides RCONH2, on the one hand, and from carbonyl compounds or their derivatives (oxidation level equal to two ), namely enamines 3, acetylenes 5, or vinyl ethers 6, on the other. Indeed, the acetylenes 5, being the dehydration products of enols, may be regarded as having a masked carbonyl functionwhile the enamines 3 rank with vinyl ethers, vinyl esters and enols, as the heteroanalogs of these carbonyl derivatives (see Section IV). 

Synthesis of Perfluoro(4-Carbomethoxybutyl Vinyl Ether). The parent ester was prepared from perfluoroglutaryl fluoride and hexa-fluoropropylene oxide by the reactions shown in Figure 2. This ester had a boiling point of 146 °C, and showed characteristic vinyl ether infrared absorptions at 5.42/, 5.55/. (carbonyl group), and 10.0/. (-OCH3 group). 

Intramolecular vinyl transfer from a vinyl ether to an ester has been reported. ... 

The allyl vinyl ethers are usually prepared in situ, but it is also possible to isolate the primarily formed mixed acetals or allyl vinyl ethers155-1 57. With low-boiling vinyl ethers the reaction is carried out in a sealed tube with an excess of the vinyl ether. For a tandem Claisen-rearrangc-ment-ene cyclization involving the Saucy-Marbet reaction cf. ref 158. The generation of isopropenyl ethers from esters is described in ref 159. For a related Claisen rearrangement by the reaction of 2-methoxybutadiene with ends and phenols see ref 160. 

Theil et al. developed a method for chemoenzymatic synthesis of both enantiomers of cispentacin [89]. frans-2-Hydroxymethylcyclopentanol, obtained by the sodium borohydride reduction of ethyl 2-oxocyclopentanecarboxylate, was monosilylated with tert-butyldimethylsilyl (TBDMS) chloride to afford 55. Lipase PS-catalysed transesterification with vinyl acetate in /erf-butyl methyl ether furnished the ester 56 and the alcohol 57. The deacetylated 58 was obtained by the Mitsunobu reaction with phthalimide, triphenylphosphine and diethyl azodicarboxylate (DEAD) to furnish the cis oriented 59 with inversion of configuration (not retention as mentioned in the original article) (Scheme 9). Desilylation, Jones oxidation and subsequent deprotection with aqueous methylamine gave the ( R,2S) enantiomer 5 [89]. The (15, 2/f) enantiomer was prepared by the same route from the silyl alcohol 57. 

Many other vinyl compounds that have an asymmetric carbon atom attached to the monomer at some point other than at the vinyl group itself have been polymerized. The monomers have included vinyl ethers, vinyl esters, vinyl acetals, vinyl ketones, W-vinylureas, A-vinylurethanes, JV-vinylurethanes, etc. [104]. In general, the further the resolved asymmetric atom is from the polymerizing vinyl group, the lower the optical activity of the final resin. 

The composition of vinyl chloride copolymers without functional groups influences their solubility behavior and compatibility with other paint binders. For example, copolymers with isobutyl vinyl ether or maleate esters dissolve in aromatic hydrocarbons, whereas copolymers with vinyl acetate merely swell in these solvents. Paint films formed from vinyl chloride copolymers without functional groups are heat sealable on account of their thermoplastic character. Since the films adhere poorly to nonabsorbing substrates such as metals, they are suitable as binders for strippable coatings. On account of their good chemical resistance, vinyl chloride copolymers are also extremely suitable as binders for exterior-use paints, traffic paints, and paper and foil lacquers their lack of taste and odor means that they can be used as pasteurization-resistant coatings for can interiors. 

Disubstituted vinyl silanes are epoxidized in high ee s and enantiomerically enriched 1,1-disubstituted epoxides can be obtained via the desilylation of these epoxides e.g., 18). Allylic alcohols and conjugated dienes and enynes are effective substrates (e.g. 19 and 20). ° The epoxidations of enol ethers and enol esters were also studied. The resulting epoxides (e.g., 21) from enol esters can undergo stereoselective rearrangement to give optically active a-acyloxy ketones, (5)-22 or (i )-23, under different acidic conditions. 

Hanzawa, Y, Kowase, N., Momose, S., and Taguchi, T. (1998) A Cp2TiCl2-Me AI (1 4) reagent system an efficient reagent for generation of allylic titanocene derivatives from vinyl halides, vinyl ethers and carboxylic esters. Tetrahedron, 54, 11387-11398. 

The polymers most investigated up to now are those derived from optically active a-olefins, vinyl ethers, vinyl ketones, acrylic or methacrylic esters, acrylamides, and aldehydes. As indicated in Table 4, isotactic and, in certain cases,isotactic and syndiotactic polymers have been obtained by using stereospecific processes. The stereospecific processes used with these chiral monomers are the same as those employed for producing stereoregular polymers from the corresponding achiral monomers. 

Aside from the simple alkyl-substituted five-membered cyclic carbonates many derivatives of EC have been developed in recent years that contain added functionality, that is, derivatives bearing reactive groups in addition to the carbonate ring itself Among them, there are vinyl moieties, esters, ethers, and alcohols (Scheme 24). 

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