Stereoselective Domino Carbocyclizations of γ- and δ-Cyano-N-tosylhydrazones with Alkenylboronic Acids with Formation of Two Different C(sp~3)-C(sp~2) Bonds on a Quaternary Stereocenter

摘要

A novel strategy for the synthesis of functionalized carbocycles is defined, through the cascade carbocyclization of alkenylboronic acids with δ- or γ-cyano-N-tosylhydrazones. In the reaction, two C(sp~3)-C(sp~2) bonds are formed on the former hydrazonic carbon generating an all-carbon quaternary stereocenter, and leading to cyclic ketones featuring an alkenyl side chain with complete diastereoselectivity. The processes are conducted under very simple experimental conditions, only in the presence of K_2CO_3, in 1,4-dioxane as solvent and under microwave irradiation, and have been applied for the synthesis of a wide structural variety of fused cyclopentanones and cyclohexanones. Moreover, the versatility of this methodology has been demonstrated in the structural modification of androsterone.