Preparation of seven- and eight-membered rings by carbon–carbon bond formation induced by samarium diiodide: 7-endo- and 8-endo-trig type cyclization to bicyclo[5.3.0]decanolone, bicyclo[5.4.0]undecanolone, and bicyclo[6.4.0]dodecanolone

Compounds with an enone-aldehyde/ketone were treated with SmI2 to form the bicyclic ketols, bicyclo[5.3.0]decanolones, and bicyclo[5.4.0]undecanolones, in different ratios depending on the reaction conditions (with or without different amounts of additives, low temperature or rt). The tendency to form seven-membered rings was different from that of six-membered rings and the mechanisms for these reactions are proposed. Cyclization to an eight-membered ring was attempted realizing in the yield of 26%.