New and Efficient Catalytic Route to Bicyclo[3.3.0]octa-1,5-dien-3-ones

The silylcarbobicyclization of 4,4-disubstituted 1,6-heptadiynes with tert -butyldimethylsilane catalyzed by Rh(acac)(CO) 2, Co 2 Rh 2 (CO) 12, or ( t -BuNC) 4 RhCo(CO) 4 under 50 atm of carbon monoxide gives the corresponding novel 7,7-disubstituted 2-silylbicyclo[3.3.0]octa-1,5-dien-3-ones in good yields. A possible mechanism is proposed. The unique feature of this strained skeleton is discussed on the basis of 13 C NMR and X-ray crystallographic analyses.