After the development of sulfoxide elimination as an effective method for generating carbon–carbon double bonds,[3] it was discovered that selenoxides undergo a similar process, albeit much more rapidly.
Evidence suggests that the elimination is syn; however, epimerization at both carbon and selenium (both of which are stereogenic) may occur during the reaction.
In one example, separation and warming of selenoxides 1 and 2 revealed that 2 decomposes at 0 °C, while 1, which presumably has more difficulty accessing the necessary syn conformation for elimination, is stable to 5 °C.
[6] (3)Kinetic isotope effect studies have found a ratio of pre-exponential factors of AH/AD of 0.092 for sulfoxide elimination reactions, indicating that quantum tunneling plays an important role in the hydrogen transfer process.
[9] It is sometimes used in excess, to overcome catalytic decomposition of H2O2 by selenium; however, undesired oxidation of starting material has been observed under these conditions.
[12] (6)α-Phenylseleno aldehydes, which are usually prepared from the corresponding enol ethers, are usually oxidized with mCPBA or ozone, as hydrogen peroxide causes over-oxidation.
α-Phenylseleno ketones can be prepared by kinetically controlled enolate formation and trapping with an electrophilic selanylating reagent such as benzeneselenyl chloride.
This process leads to elimination products retaining a carbon-selenium bond,[16] and is more difficult to prevent than the seleno-Pummerer reaction.
[17] (11)The combination of silyl enol ethers with palladium(II) acetate (Pd(OAc)2), the Saegusa oxidation, gives enones.