Vinyl epoxides simple

Interestingly, in DMF as solvent and with C032-, for 24 a cyclization leading to the corresponding vinyl epoxides 26 [24] could be achieved Simple treatment of 24 with Ag1 delivers 25. The silver] I [-catalysts show significant lower reactivity, thus usually 20 mol% or even more are applied. 

Vinyl epoxides can also be used as substrates for formation of optically active allyl amines catalyzed by the same type of chiral palladium complexes as in Eq. (10). By reaction of simple vinyl epoxides with phthalimide as the nitrogen source in the presence of the chiral palladium complexes as the catalyst, very high ee (> 98 %) and regioselectivity (> 97 %) were obtained [26]. A variety of different applications of the use of the palladium-catalyzed approach for the formation of allyl amines and the use of this in total synthesis has been pursued by several research groups, and further details can be obtained in a review by Trost et al. [19d]. 

In the course of our earlier studies on terpenylboranes we developed a simple transformation of a- into 3-pinene," and a stereoselective synthesis of allylic alcohols by the reduction of vinylic epoxides.12 An extension of these studies to contrathermo-dynamic isomerization of a-thujene, 2- and 3-carene,13 and kinetic resolution of vinylic epoxides by the reduction with terpenylboranes,14 is described. 

Kinetic resolution of vinylic epoxides by the reduction with terpenyl dialkylboranes of high optical purity is a simple and direct method for the preparation of enantiomerically enriched epoxides. It allows for convenient configurational assignment of epoxides if the configuration of the corresponding allylic alcohol is known. Both enantiomers can be prepared using readily available enantiomeric diisopinocampheylboranes. 

Bandini, M., Cozzi, P. G., Melchiorre, P., Morganti, S., Umani-Ronchi, A. Cr(Salen)-Catalyzed Addition of 1,3-Dichloropropene to Aromatic Aldehydes. A Simple Access to Optically Active Vinyl Epoxides. Org. Lett. 2001, 3,1153-1155. 

Relative reactivities 254 Simple vinyl epoxides 255 Cyclic vinyl epoxides 257... 

Ethylene oxide and simple primary and secondary epoxides 271 Tertiary epoxides 272 Acetals and epoxy ethers 272 Vinyl epoxides 273... 

Simple alkyl epoxides 277 Arene oxides 277 Cyclic vinyl epoxides 279... 

Monoepoxides of simple cyclic 1,3-dienes are smoothly converted in good yield to /3,y-unsaturated ketones in the presence of Pd(Ph3P)4 catalyst (eq 47). Other vinyl epoxides, such as those in open chains or in cyclic systems in which the double bond is not in the ring, are converted under similar conditions into dienols. 

The synthesis of vinyl epoxides from dienes is mentioned in Chapter 19. The monoepoxide is formed first as the diene is more nucleophilic than the alkene in the monoepoxide. The main difficulty is that the monoepoxide rearranges with acid catalysis from the by-product, the carboxylic acid of the peroxyacid used in the epoxidation. The solution is simple the mixture must be buffered to keep the acidity low. 

Bandini M, Cozzi P-G, Melchiorre P, Morganti S, Umani-Ronchi A. Cr(Salen)-catalyzed addition of 1,3-dichloropro-pene to aromatic aldehydes. A simple access to optically active vinyl epoxides. Org. Lett. 2001 3 1153-1155. 

Vinylic sulfides containing an a hydrogen can also be alkylated by alkyl halides or epoxides. This is a method for converting an alkyl halide RX to an a,P unsaturated aldehyde, which is the synthetic equivalent of the unknown HC=CH—CHO ion. Even simple alkyl aryl sulfides RCH2SAr and RR CHSAr have been alkylated a to the sulfur. ... 

By analogy to simple olefins, we propose that 0(3P) initially adds to the 1,4 or 1,2 double bonds in polybutadienes at ambient temperature. Since the rate constants for 0(3P) addition to cis-2-butene and 1-butene (as models for 1,4 and 1,2 double bonds, respectively) are in the ratio 4.2 1 at 298 K ( 6), preferential addition to the 1,4 double bonds is assumed to persist to very high vinyl contents (-8011). The biradical adducts then rearrange to epoxides and carbonyl compounds or give rise to chain rupture and/or crosslinking as a consequence of PIF, according to the scheme ... 

Vinylic organocuprates, prepared by transmetallation of vinylic tellurides with Bu (2-Th)Cu(CN)Li2, are highly reactive towards simple epoxides. ... 

A catalytic amount of ketone 26 was used to investigate the substrate scope of the asymmetric epoxidation. High enantioselectivities can be obtained for a wide variety of trans- and trisubstituted olefins (Table 3, entries 1 ) [54]. Simple trans-olefins, such as franx-7-tetradecene, can be epoxidized in high yield and enantiomeric excess, indicating that this asymmetric epoxidation is generally suitable for frani-olefms. 2,2-Disubstituted vinyl silanes are epoxidized in high ees (Table 3, entries 5, 6) and enantiomerically enriched 1,1-disubstituted epoxides can be... 

That ethylene oxide can react directly with oxonium ions is shown by its reaction with triethyl oxonium borofluoride but this reaction, because of its complexity, does not shed much light on the polymerization. The sole product is dioxane and the vinyl ether colors appear only after all epoxide has reacted. Initial rates suggest first order in catalyst but the first order plots of monomer disappearance are flat S-curves suggesting a rate which first falls off, then tends towards zero order. The first step in the reaction is most probably a simple bimolecular alkylation of the epoxide by oxonium salt but the subsequent steps are obscure. The simplest path would be... 

From patent literature, it appears that Vandenberg (353) was the first to polymerize vinyl ethers to crystalline polymers using modified Ziegler catalyst preparations. A series of papers have been published by Vandenberg and his associates which describe the polymerization of simple alkyl vinyl ethers (29), ROCH=CHCHs (354), CH30CH=CH--CH=CH2 (355), and epoxides (356). 

It is all true. Evidence that a silyl group stabilizes the S 2 transition state comes from the reactions of the epoxides of vinyl silanes. These compounds can be made stereospecifically with one equivalent of a buffered peroxy-acid such as m-CPBA. Epoxidation is as easy as the epoxidation of simple alkenes. You will see in a moment why acid must be avoided. 

Pradilla et al. have shown that simple p-tolyl vinyl sulfoxides undergo nucleophilic epoxidation with metal alkyl peroxides to give enantiopure sulfinyl oxiranes.138 This process takes place with fair to excellent diastereoselectivities. The same group recently reported the epoxidation of diastereomeric hydroxy vinyl sulfoxides, bearing an additional stereocenter adjacent to the reactive carbon-carbon double bond. Hydroxy vinyl sulfoxides 256 and 258 underwent epoxidation with lithium ferf-butyl peroxide with high anti selectivity. However, when potassium ferf-butyl peroxide was used, only hydroxy vinyl sulfoxide 256 showed anti... 

The discussion above emphasizes that the allyl-Ni reagents are quite selective for carbon halogen bonds, especially allyl, vinyl, and aryl halides. At the same time, modest reactivity as nucleophiles toward reactive carbonyl derivatives has been reported.Simple aldehydes, the more reactive ketones (such as cyclopentanone and benzoquinone), and certain epoxides will undergo 1,2-addition of the aUyl ligand to the carbonyl group. Esters, amides, and, most remarkably, acyl halides are inert toward the allyl Ni reagents under conditions where the reagents do not decompose thermally (<80 °C or so). 

---