Synthesis of Functionalized 6-(Pyridyl)salicylates, Bis(benzophenones), Chlorinated 6H-Benzo[c]chromen-6-ones, 9H-Fluoren-9-ones, Isobenzomorphans and Dibenzo[b,d]pyrid-6-ones based on New Cyclocondensations of 1,3-Bis(silyloxy)-1,3-butadienes

Abstract

Regioselective 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. 6-(Pyridyl)salicylates and biaryls are prepared based on [3+3] cyclocondensations of 1,3-bis(silyl enol ethers) and 1-aryl-1-silyloxy-1-en-3-ones. Subsequently, 2-methoxy- and 2-nitro-substituted biaryls are transformed into biaryl lactones and 6(5H)-phenanthridinones based on a lactonization and lactamization strategy, respectively. Furthermore, some of the biaryls are also converted to the respective fluorenones by Friedel–Crafts acylations. The cyclocondensation reaction of aryl-1,3-bis(silyl enol ethers) with 3-formylchromone yielded bis(benzophenones). In addition, functionalized 7,8-benzo-9-azabicyclo[3.3.1]nonan-3-ones (isobenzomorphanons) have been prepared by cyclocondensation of aryl-1.3-bis(silyl enol ethers) with isoquinolines.