Alcoholysis of epoxides

An interesting alcoholysis of epoxides has been reported by Masaki and coworkers <96BCSJ195>, who examined the behavior of epoxides in the presence of a catalytic amount of the Tt-acid tetracyanoethylene (TCNE, 85) in alcoholic media. Ring-opening is very facile under these conditions, typically proceeding via normal C-2 attack, as exemplified by styrene oxide (86). Certain epoxy ethers (e.g., 89) undergo C-1 attack due to anchimeric assistance. Analysis of the reaction mixtures revealed the presence of captodative ethylenes (e.g., 85) formed in situ, whieh were shown to be aetive in eatalyzing the reaction. The proposed mode of catalysis is represented by the intermediate 87. The affinity of these captodative olefins for... 

Next to iodine there is also another class of neutral Lewis acids known. Tetracyanoethylene, dicyanoketene acetals and derivatives can catalyse reaction due to their tt-Lewis acid properties. They promoted the alcoholysis of epoxides [238], tetrahydropyranylation of alcohols [239], monothioacetahzation of acetals [240], and carbon-carbon bond formation of acetals [241,242] and imines [243] with silylated carbon nucleophiles. 

H3PW12O40 shows a higher activity for the alcoholysis of epoxides [Eq. (15)] than H2SO4, PTS, or HCIO4 (9, 124, 175). While rapid deactivation is observed with H2S04, which is probably due to the formation of an alkyl sulfate, H3PW12O40 maintains its high catalytic activity. 

Ring cleavage. Catalyzed hy Sc(OTf)3, alcoholysis of epoxides and aziridines proceeds at room temperature. The ring opening of mei oepoxides is rendered asymmetric if a chiral ligand such as 1 is added to the reaction medium. Lactones give polymers via alcoholysis. ... 

Alcoholysis of epoxides. FeCl-. is Oxidative cleavage of trimethyhU generation, in combination with conjugal Smith reaction, completes the sequence substituent at the y-position of a lower h readily prepared from cyclopentenone. 

Alcoholysis of epoxides. Epoxide opening with alcohols to afford monoethers of 1,2-diols is promoted by TCNE at room temperature. 

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