| 摘要 |
The preparation, as per EP648722, of substituted cyclopentadienes by reaction of Grignard reagents with cyclopent-2-ene-1-ones substituted in at least the 3-position is modified by effecting the protonization and dehydration in one step without use of water or aqueous acids by adding an alcohol to the Grignard addition product. Preparation of substituted cyclopentadienes of formula (IA) and (IB) comprises: (A) reacting a substituted cyclopent-2-ene-1-one of formula (II) with a Grignard reagent of formula R<2>(R<3>)CHM (III) in an inert organic solvent to give a compound of formula (IV); and (B) adding a stoichiometric or sub-stoichiometric amount of an alcohol of formula R<7>OH (V) to give an organic phase containing the compounds (IA) and (IB). R = 1-20C hydrocarbyl such as optionally substituted alkyl, alkenyl, cycloalkyl, aryl, aralkyl or alkaryl, preferably 1-10C alkyl or 6-10C aryl, and especially methyl or phenyl; R<2> and R<3> = H or 1-20C hydrocarbyl such as 1-10C alkyl or 6-10C aryl, especially H or 1-8C alkyl; R<4> - R<6> = especially H, but can also be 1-20C hydrocarbyl such as 1-10C alkyl or 6-10C aryl; M = MgCl, MgBr or MgI; and R<7> = 1-20C hydrocarbyl such as 1-10C alkyl (especially preferred), 6-10C aryl or 7-10C aralkyl.
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