Synthesis of 3-alkyl-5-hydroxycyclohex-2-enones via aldolic addition/sulfinate elimination tandem reactions

Highly Efficient Formal Synthesis of Cephalotaxine, Using the Stevens Rearrangement−Acid Lactonization Sequence as A Key Transformation

“…To our delight, Swern oxidation of diol 18 produced the stabilized amido keto-aldehyde 19 in almost quantitative yield. The treatment of 19 with K 2 CO 3 , under MeOH-H 2 O conditions, produced the amido spirocyclopentenone 3b . According to Li et al’s procedure, triflic acid mediated Friedel−Crafts cyclization of amido spirocyclopentenone 3b furnished 2b , whose spectra ( 1 H NMR, 13 C NMR, IR) were in full accord with those reported by Hanaoka et al The modified sequence outlined in Scheme constitutes a highly efficient formal synthesis of CET.…”