An alternative approach to α-methylene lactone

✍ Scribed by Y. Jenkitkasemwong; Y. Thebtaranonth; N. Wajirum

• Publisher: Elsevier Science
• Year: 1979
• Tongue: French
• Weight: 207 KB
• Volume: 20
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)93606-8

✦ Synopsis

Model syntheses of a-methylene-y-butyrolactones have been achieved via an alkylationlactonlsatlon reaction of anthracene adducts la and lb with epoxides followed by release of the -methylene lactones through a retro Duels-Alder reactjon Numerous reports concerning the synthesis of a-methylene lactones have appeared In the literature and constructing the methylene group Itself has claimed its own field of research (1) Lately, the masked acrylate anion has caught interest as a good candldate for the methylene synthon and its application 1s belpg studied by several groups (2) We have formerly noticed that upon treatment with LDA (1 2 equivalent) at 0' in THF/ TMEDA (8/l) adducts @ and &(3) gave orange solutions of anions 2a and 2b which could then be -alkylated with alkyl halides to give products 3a and 3b respectively --1 2 3 _ -a,R=H b_, R = COOMe The sequence greatly appealed to us because the anlon g 15, in fact, an easily avallable form of masked acrylate anion, provldlng that 3 will undergo a retro Diels-Alder reaction. -1Je have now proved this to be the case, and wish to report in this communication our fIndings (4) The reaction of the anion 2a with gaseous ethylene oxide at room temperature for 5 hr. in THF/T"1EDA (8/l) gave a good yield of 4a -(5) (mp 112-4', m/e 276, ir.1750 cm-', 72%) Similarly, treatment of 2b with the same reagent produced a crude mixture, which, upon separatior by preparative TLC (using CHC13/hexane=3/2 as the developing solvent) two isomerlc products, asslgned as 4b cls (mp. 257-259 5' sublimed, m/e 334, ir 1760,1733 cm-l) and 4b trans (mp. 203-204 5', m/e 334, lr.1765,1720 cm-') were isolated in a rat.10 of 1 2 (80% purlfled yield) (6) 1615