LE>left" HSPACE=5> |
Functionalized dibenzo[
b,
d]pyran-6-ones were prepared byformal [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with3-silyloxy-2-en-1-ones or 1,1-diacetylcyclopropane to givefunctionalized salicylates, Suzuki cross-coupling reactionsof the corresponding triflates, and subsequent BBr
3-mediatedlactonization. A second approach to dibenzo[
b,
d]pyran-6-ones relies on the [3 + 3] cyclization of 1,3-bis(silyl eno
lethers) with 1-(2-methoxyphenyl)-1-(trimethylsilyloxy)alk-1-en-3-ones and subsequent BBr
3-mediated lactonization.