The Ramberg–Bäcklund Rearrangement
1991; Elsevier BV; Linguagem: Inglês
10.1016/b978-0-08-052349-1.00084-6
Autores Tópico(s)Inorganic and Organometallic Chemistry
ResumoIn 1940, Ramberg and Bäcklund reported a new and surprising reaction, i.e. that on treatment with an excess of aqueous KOH, α-bromoethyl ethyl sulfone was converted in high yield into 2-butene (equation 1).1 α-Chloroethyl ethyl sulfone reacts in the same way, although more slowly. Also surprising was the stereoselectivity of this reaction; bromination of the 2-butene was found to give racemic 2,3-dibromobu- tane, showing that the (Z)-isomer predominated. Since that time, this transformation, now known as the Ramberg-Bäcklund rearrangement, or simply as the Ramberg–Bäcklund reaction, has been used to syn- thesize a wide variety of alkenes. It is now understood to take place via 1,3-elimination of halide from the sulfone α-anion, and loss of SO2 from the resulting thiirane 1,1-dioxide (Scheme 1).
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