Alkoxy elimination

The reaction may proceed via the hydroalumination of the olefin moiety to give 15, which can undergo [3-alkoxy elimination to yield, upon workup, the alcohol 16. How-... 

The P-alkoxy elimination pathway is important during the incorporation of oxygen-containing monomers. Therefore, it is often necessary to provide distance between the olefin and the polar group, or to prevent chain walking close to the group that can be eliminated by the placement of a quaternary carbon spacer [87], The incorporation of acrolein dimethyl acetal is accompanied by reduced activity and full catalyst... 

Very recently, Murakami has published an Rh(i)-catalyzed cyclization of 1,6-enynes triggered by addition of arylboronic acids (Scheme 74).281 Initial carborhodation of the alkyne moiety is followed by insertion into the alkene moiety. /3-Alkoxy elimination provides the final product 289 in good yield and regenerates the catalyst species. 

Cleavage of Ethers to Olefins Hydro-alkoxy-elimination... 

Typical values given in the literature for Lyocell dopes without stabilizers added are DP losses from 472 to 177 over 6 hours at 105 °C [22], or from 570 to 185 over 2 hours at 90 °C [23]. The activation energy for the cellulose chain cleavage in NMMO at temperatures above 115 °C was determined to be 69 kj/mol. This observation strongly supported the hypothesis that the actual rate-determining step of the cellulose chain cleavage was a /1-alkoxy elimination, with an activation energy of 67-72 kj/mol [24,25]. 

Fig. 2-33. Alkaline peeling reaction of cellulose (R = cellulose chain). 1 — 2, Isomerization 2 — 3, 2,3-enediol formation 3 — 4, j3-alkoxy elimination 4 —> 5, tautomerization 5 — 6, benzilic acid rearrangement leading to glucoisosaccharinic acid.

N-Alkoxymethyl(trimethylsilyImethyl)amines are convenient precursors for C-unsubstituted azomethine ylides 43 since the N-alkoxymethyl(trimeth-ylsilylmethyl)amines are readily available by the reaction of N-alkylated silylmethylamines with formaldehyde in alcohol solvents (84CL1117). Treatment of the amines with trimethylsilyl triflate in acetonitrile or tetrahy-drofuran brings about the elimination of alkoxy group R O to form N-silylmethyliminium trifiates 42. The subsequent desilylation with cesium fluoride generates C-unsubstituted azomethine ylides 43 (84CL1117). Both steps of the alkoxy elimination and subsequent desilylation of 42 are induced by trifluoroacetic acid (85CPB896, 85CPB2762), tetrabutylammonium... 

The enolate ion (XXXV), formed from a carbonyl group at either C2 or C3, is the same ion that is the active participant in the alkaline degradation of polysaccharides by the -alkoxy carbonyl mechanism. Hence, it has been postulated that oxidized polysaccharides of the keto (carbonyl) type are degraded in alkali by an alkoxy-elimination reaction. The chains... 

Heterocycles have also been prepared from substrate substructures F (Figure 6.4). Sinou and coworkers [102] reported the synthesis of enantiopure cw-fused pyrano[2,3,c]pyrans from the corresponding glycals via an intramolecular Mizoroki-Heck cyclization either followed by classic -hydride or by jS-alkoxy elimination (Scheme 6.37). 

Scheme 6.37 Synthesis of pyrano[2,3,c]pyrans through classic fi-hydrogen or via fl-alkoxy elimination.

BedjegueM, K., Bolitt, V. and Sinou, D. (1999) Intramolecular Heck cycUsation-)3-alkoxy elimination in carbohydrate chemistry. A simple route to enantiopure annelated dioxatricyclic compounds. Synlett, 762-4. 

Saturated acyclic imides Consecutive CO (Am 28) and alkoxy elimination + ... 

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