New synthesis of Triarylmethanes, Pyranones, Indoles and Pyrroles: Cyclization reactions at their best

Dianions and masked dianions represent important building blocks for the regioselective formation of carbon-carbon bonds. Cyclocondensation reactions of 1,3-bis(silyl enol ethers) with different mono(silyl enol ethers) provide an elegant approach for the synthesis of various complex carba- and heterocycles from simple starting materials. A variety of functionalized and sterically encumbered triarylmethanes were prepared by combination of FeCl3-catalyzed benzylations of 1,3-diketones and formal [3+3] cyclocondensation reactions of 1,3-bis(silyl enol ethers) and 3-benzyl-1-silyloxy-1-en-3-ones. Subsequently, 4-methoxy-, 4-chloro and 4-flulro-substituted triarylmethanes are prepared The products are not readily available by other methods. In addition, functionalized diarylmethanes have been also prepared by cyclocondensation of 1.3-bis(silyl enol ethers) with with respective 3-benzyl-1-silyloxy-1-en-3-ones. Further more, dianions were converted to useful cyclic structure of pyranones with functionalized benzaldehydes providing a new strategy. Varius pyranones were synthecized containing 3-bromo-, 4-Methyl-, 4Phenyl-, 4-methoxy- and 4-hydoxy-phenyle groups.