Acorenone precursor

An intramolecular cycloaddition of an a diazoketone, a reaction which has featured prominently this year, forms the key step, (250) - (251), in a synthesis of solavetivone. By contrast, intramolecular cycloadditions of car-benoids derived from a-diazoketones have been used in total synthesis of ( )-a-chamigrene and (-)-acorenone B in the latter case, (+)-limonene was used as the chiral precursor. ... 

The addition of carbanions on the complex [Cr(T] -o-methylanisole)(C0)3] (see Chap. 10) leads, after a second nucleophilic attack of the same type followed by decomplexation, to a spiranne precursor of acorenone. The methoxy substituent has a remarkable meta-directing effect. ... 

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