767332-39-8Relevant articles and documents
Internal nucleophilic termination in acid-mediated polyene cyclizations part 3. Synthetic access to didehydro and methyl didehydro analogues of (±)-ambrox
Snowden, Roger L.,Eichenberger, Jean-Claude,Linder, Simon,Sonnay, Philippe
, p. 1711 - 1723 (2007/10/03)
Treatment of the unsaturated allenic alcohols (E)-7, (Z)-7, 10, 13, and 19 with an excess of FSO3H in 2-nitropropane at -90° to -30° afforded, in 68-85% yield, diastereoisomer mixtures of racemic tricyclic ethers 14a-d and 20a-d, respectively (Schemes 3 and 5), with high stereoselectivity (see Table and Scheme 6). These stereospecific transformations represent the first reported examples of an acid-mediated polyene cyclization, in which an alkene is the initiating group and an allenic alcohol serves as the internal terminator. In close analogy to our earlier work, a nonsynchronous process is postulated, whereby the stereochemical course of cyclization is directed by the conformational structure of an intermediate cyclohexyl cation (see Schemes 3 and 6). In addition, the organoleptic properties of 14c and 20c, racemic didehydro and methyl didehydro analogues, respectively, of the known odorant Ambrox ((-)-4f), are briefly discussed.
