Claisen rearrangement based methodology for the spiroannulation of a cyclopentane ring. Formal total synthesis of (+/-)-acorone and isoacoromes

A Claisen rearrangement based methodology for spiroannulation of a cyclopen tane ring to cyclic precursors and its application in the formal total synt hesis of acorones 1 is described. Thus, Claisen rearrangement of 2-cycloalk ylideneethanols 12 with 2-methoxypropene and a catalytic amount of mercuric acetate generates 4,4-substituted hex-5-en-2-ones 13. Ozonolytic cleavage of the terminal olefin in the enones 13 and intramolecular aldol condensati on of the resulting keto-aldehydes 14 furnishes the spiroannulated compound s 15. (C) 2000 Elsevier Science Ltd. All rights reserved.