26806-12-2Relevant articles and documents
Acetoxyselenenylation of Olefins for the Preparation of Vinylic and Allylic Acetates
Engman, Lars
, p. 884 - 890 (2007/10/02)
Terminal and 1,2-disubstituted olefins were irreversibly acetoxyselenenylated by treatment with PhSeBr in an acetate buffer solution.Styrene derivatives yielded only Markovnikov adducts whereas simple terminal olefins and olefins containing an allylic oxygen substituent (acyloxy or aryloxy group) afforded significant amounts (50-85percent) of the anti-Markovnikov isomer.The product mixtures were isomerized to contain 90-97percent of the Markovnikov products by treatment with a catalytic amount (6-41percent) of BF3*OEt2 in chloroform.Oxidation (SO2Cl2/hydrolysis or MCPBA) of the isomerized products and selenoxide elimination at elevated temperature toward the acetoxy group afforded enol acetates in fair yields.The selenoxides of the anti-Markovnikov isomers (unisomerized mixtures) spontaneously eliminated, in the presence of the selenoxides of the Markovnikov isomer, to give allylic acetates in good yields at ambient temperature.
METAL-CATALYZED REARRANGEMENTS OF ALLYLIC ESTERS
Oehlschlager, A. C.,Mishra, P.,Dhami, S.
, p. 791 - 797 (2007/10/02)
It has been shown that Pd(CH3CN)2Cl2 catalyzes the rearrangement of allylic esters.Carbamates rearrange more rapidly than acetates which in turn rearrange more rapidly than carbonates.Allylic carbamates are more rapidly isomerized by Pd(CH3CN)2Cl2 than by Hg(OCOCF3)2.The rearrangement proceeds well except in cases where the central carbon of the allylic system is fully substituted.In contrast to the reported rearrangement of allylic carbamates by Hg2+ and previous reports of Pd2+-catalyzed rearrangements of allylic esters, this work showed the latter are extremely E specific; thus E allylic acetates yield equilibrium mixtures free of Z allylic isomers, under conditions in which Z allylic acetates are unreactive.This E specificity is applied to stereospecific 1,3-diene synthesis from bis E,Z-allylic acetates