Ethers alkenyl

Exchange Reactions of Alkenyl Ethers and Esters Catalyzed by Pd(II)... 

The key step in the total synthesis of rhizobitoxine is the Pd-catalyzed exchange reaction of the methyl alkenyl ether moiety in 4 with the functionalized alcohol, although the yield is low[3]. The enol pyruvate 6 (a-ethoxyacrylic acid) is prepared by the reaction of methyl a-methoxyacrylate or a-methoxy-acrylic acid (5) with ethanol catalyzed by PdCl2(PhCN)2 at room temperature in the presence of CuCli and NaH2P04[4],... 

Simple alkyl and alkenyl ethers of pentaerythritol are produced on direct reaction of the polyol and the requited alkyl or alkenyl chloride in the presence of quaternary alkylamine bromide (44). AHyl chloride produces the pentaerythritol tetraHyl ether [1471 -18-7],... 

Perfluoroallyl fluorosulfate is prepared by the treatment oiperfluoropropene with sulfur tnoxide m the presence of boron catalysts [2, 3, 4, 5, 6, 7] (equation 2) Perfluoroisopropyl allyl ether reacts similarly to give 58% polyfluoroallyl fluorosulfate in a cis/trans ratio of 6 4 [S] Sultones are the exclusive products without catalyst. Polyfluoroolefins such as 2-hydropentafluoropropylene [9], (2,3-dichloropropyl)tri-fluoroethylene [70], perfluoropropene [2, i], perfluoroisopropyl alkenyl ethers [S], and acyclic polyfluoroallyl ethers [77] undergo sulfur trioxidation to regioselectively produce the corresponding P-sultones in high yield... 

Enol ethers are found in this section as well as alkenyl ethers. 

The intramolecular addition of the O-H bond to alkynes catalyzed by palladium complexes has been developed by K. Utimoto et al. (Eq. 6.59) [104]. An alkynyl alcohol can be converted to a cyclic alkenyl ether in the presence of a catalytic amount of [PdCl2(PhCN)2 or [PdCl2(MeCN)2] in ether or THE at room temperature. When the reaction was carried out in MeCN-H20 under reflux in the presence of a catalytic amount of PdCl2, hydration of the acetylenic alcohol occurred and the ketoalcohol was obtained in good yield instead. 

Aryl/Alkenyl Ether Formation via Cross-Coupling Reactions 650... 

As the representative examples in Scheme 6.11 illustrate, similar stragies may be applied to the corresponding alkenyl ethers (vs. styrenyl ethers) [26], The Zr-catalyzed kinetic resolution/Ru-catalyzed metathesis protocol thus delivers optically pure 2-substituted di-hydrofurans that cannot be accessed by resolution of the five-membered ring heterocycles (see Scheme 6.8). It should be noted, however, that the efficiency of the Zr-catalyzed resolution is strongly dependent, and not in a predictable manner, not only on the presence but the substitution of the acyclic alkene site of the diene substrate. The examples shown in Scheme 6.11 clearly illustrate this issue. 

The same type of addition—as shown by X-ray analysis—occurs in the cationic polymerization of alkenyl ethers R—CH=CH—OR and of 8-chlorovinyl ethers (395). However, NMR analysis showed the presence of some configurational disorder (396). The stereochemistry of acrylate polymerization, determined by the use of deuterated monomers, was found to be strongly dependent on the reaction environment and, in particular, on the solvation of the growing-chain-catalyst system at both the a and jS carbon atoms (390, 397-399). Non-solvated contact ion pairs such as those existing in the presence of lithium catalysts in toluene at low temperature, are responsible for the formation of threo isotactic sequences from cis monomers and, therefore, involve a trans addition in contrast, solvent separated ion pairs (fluorenyllithium in THF) give rise to a predominantly syndiotactic polymer. Finally, in mixed ether-hydrocarbon solvents where there are probably peripherally solvated ion pairs, a predominantly isotactic polymer with nonconstant stereochemistry in the jS position is obtained. It seems evident fiom this complexity of situations that the micro-tacticity of anionic poly(methyl methacrylate) cannot be interpreted by a simple Bernoulli distribution, as has already been discussed in Sect. III-A. 

The alkenylation of phenols also proceeds smoothly in the presence of TMG (Scheme 6). The major products are not aryl alkenyl ethers but a-alkenylated cyclohexa-2,4-dienones. That is, C-alkenylation occurs exclusively at the ortho position of phenols. When 2-naphthol reacts with two equivalents of the alkenylbismuthonium salt, a,a-dialkenyl ketone is obtained in good yield as the sole alkenylated product. 

Schwartz (1972) also noted the detection of about 70 glycerol-l-alkyl ethers in milk fat. Saturated ethers, both odd and even from C-10 through C-18, were found, with traces of ethers up to C-25 present. Fifty-five unsaturated ethers were separated, but only the A-9, A-9, 12, and A-9, 12,15 compounds were tentatively identified. In addition, Schwartz isolated over 50 bound aldehydes probably derived from the glycerol-l-alkenyl ethers (phosphorus free). 

Hay and Morrison (1971) did not neglect the alkyl and alkenyl ethers in milk phospholipids, finding 4% of the latter in phosphatidylethanolamine and 1.3% in phosphatidylcholine. Trans isomers were not found. The authors postulated that the branched chain compounds in the alkenyl ethers were derived from rumen microbial lipids. 

Hay, J. D. and Morrison, W. R. 1971. Polar lipids in bovine milk. III. Isomeric cis and trans monoenoic and dienoic fatty acids, and alkyl and alkenyl ethers in phosphatidyl choline and phosphatidyl ethanolamine. Biochim. Biophys. Acta 248, 71-79. 

Alkyl and alkenyl ethers have been identified in phosphatidyl choline and phosphatidyl ethanolamine fractions recovered from whole milk (Hay and Morrison 1971). To our knowledge, levels of alkyl and alkenyl ethers in phospholipids of milk lipid globule membrane have not been measured. 

Ether phospholipids, analogous to the ether lipids described in Section 2, are also widely distributed. Tire alkenyl ether analogs of phosphatidylcholine (Fig. 8-2) are called plasmalogens.17 In neutrophils the 1-O-alkyl ethers contain the major share of the cell s arachidonic acid, which is esterified in the 2 position.1819... 

Cinnamyl—sesamol ethers, eg (35), are useful as insect chemosterilants (111). 3,4-Methylenedioxyphenyl-3-lialo-2-propynylethers (36, X = halogen) are synergists for carbamate insecticides (112). Haloalkyl or halo alkenyl ethers, eg (37), show acaricidal and insect juvenile hormone activity (113). The first total synthesis of gibbereUic acid was from 2-methoxy-6-alkoxyethyl-l,4-benzoquinone, a derivative of hydroxyhydroquinone (114). 

It has been shown in ozonizations of fluoroalkenes (vide supra) that fluoro substituents stabilize the ozonides formed from the rearrangement of the initial molozonides. Rather stable ozonide isomers 3 are formed from the trifluoromethylated alkenyl ether 2 as two separable dia-stereomers with isolated yields 27 and 26%. respectively.180 The stability was demonstrated... 

Cross-coupling of organoalanes with ally lie acetals or ortho esters (cf., 10, 388).6 The Pd(0)-catalyzed coupling of alkenylalanes with 1 proceeds with exclusive attack at the y-position to provide alkenyl ethers. 

Alkenyl ethers (enol ethers) of the type ROCH=CH2 are more stable to rearrangement to 0=CH—CH2R than is an enol such as HOCH=CH2to 0=CH—CH3. Why What conditions would you expect to be favorable for rearrangement of an alkenyl ether ... 

The nature of the oxidation products is traceable to the nature of the rhodium-alkene interaction. Terminal alkenes and internal ones (e.g. cycloheptene), which form 77-complexes of rhodium(I), e.g. [RhCl(alkene)2]2, are selectively converted into methyl ketones, whereas alkenes which form 7r-allylic complexes of rhodium(III) (e.g. cyclopen-tene) give alkenyl ethers via oxidative substitution of the alkene by the solvent alcohol.204... 

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