New synthesis of (±)-karanone, an important aroma compound in agarwood.

A concise synthesis of (±)-karanone, an important aroma compound of agarwood, was achieved from a commercially available 3-methylcyclohex-2-enol in 3.5% yield in 11 steps. The two contiguous stereocenters at C4 and C5 were constructed via Ireland-Claisen rearrangement. The allylic oxidation at C8 was successfully performed with the mixture of tert-butyl hydroperoxide (TBHP) and CuI. A precursor of ring-closing metathesis to construct a bicyclic dienone was efficiently synthesized from iodoenone by 1,4-addition and nucleophilic substitution of the vinyl group in one pot.