A highly efficient methylenecyclopentane annulation process has been developed based on the Pd(II)-mediated oxidative cyclization of omega-unsaturated alpha-cyano ketones, readily accessed via the Michael addition of 3-butenylmagnesium bromide with 2-cyano-2-cycloalkenones.

Ring closure reactionsRing closure reactions O 0130 Palladium(II) Acetate Mediated Oxidative Cyclization of ω-Unsaturated α-Cyano Ketones. A Facile Methylenecyclopentane Annulation Process. -ω-Unsaturated α-cyano ketones, readily available via the Michael addition of 3-butenylmagnesium bromide (II) with 2-cyano-2-cycloalkenones undergo an efficient methylenecyclopentane annulation process to give bicyclic α-cyano ketones. -(KUNG, L.-R.; TU, C.-H.; SHIA, K.-S.; LIU*, H.-J.; Chem.

An operationally simple and highly effective annulation process, making use of ZnCl 2 -catalyzed Michael addition and K 2 CO 3 /NaI-induced cyclization as key manipulations, has been developed to construct various bicyclic systems with a high level of functionalization valuable for further synthetic elaboration.

The DBU‐catalyzed stereoselective annulation reaction of cycloalkenones with the Nazarov reagent delivers a range of bicyclic compounds possessing a high degree of oxygenated functionality.

K 2 CO 3 /NaI-Induced Cyclization of ω-Bromo α-Cyano Ketones: A New Annulation Approach for the Formation of Carbalkoxycyclohexane Ring System. -The construction of various bicyclic systems is achieved using a two-step sequence which involves Michael addition of lithium enolates (II) to cycloalkenones and subsequent cyclization of the resulting ω-bromo-α-cyano ketones. The smaller ring systems are formed with cis-junction, whereas trans-junction is observed for the higher ones. The sterically defined, highly substituted products are suitable for further functionalizations. -(TU, C.-H.; SHIA, K.-S.; KUO, S.-C.; LIU*, H.-J.; HSIEH, M.-T.; Synlett 2012, 11, 1653-1656, http://dx.