Mercury(II)-catalyzed synthesis of spiro[4.5]decatrienediones in the presence of water

Article abstract of DOI:10.1016/S0040-4039(98)02057-7

Treatment of the easily available p-methoxybenzyl allenyl ketone 2 or the (p-tert-butyldimethylsiloxybenzyl) allenyl ketone 9 with 1% Hg(ClO₄)₂ in acetonitrile/water provided good yields of the spiro[4.5]deca-3,6,9- triene-2,8-dione 6c. The Hg(II)-catalyzed addition of water to the allene was much slower, the 1,3-diketone 7 was only a minor side-product. The isomeric o-methoxybenzyl allenyl ketone 12 formed some spiro[4.5]deca-3,7,9-triene- 2,6-dione 13, the side-reactions were the addition of water and a new spirocyclization/dimerization leading to 15.