%0 Journal Article %A Wang, Lihong %A Prabhudas, Bodhuri %A L. J. Clive, Derrick %D 2009 %T Formation of Carbocycles by Intramolecular Conjugate Displacement: Scope and Mechanistic Insights %U https://acs.figshare.com/articles/journal_contribution/Formation_of_Carbocycles_by_Intramolecular_Conjugate_Displacement_Scope_and_Mechanistic_Insights/2860978 %R 10.1021/ja900857h.s001 %2 https://ndownloader.figshare.com/files/4558804 %K allylic position %K intramolecular addition %K material %K substituent %K proton source %K THF %K Cs 2CO %K DBU %K displacement %K Intramolecular Conjugate Displacement %K Michael acceptor unit %K ring closure %K formation %K Michael acceptor subunit %K Michael acceptors %K carbanion %K Michael addition %K transition metal %K CN %K CP %K SN %K ICD reactions %K Michael acceptor %K reaction conditions %K mechanism %K Mechanistic InsightsA %K CO 2R %X A detailed study has been made of a method of ring closure categorized as an all-carbon intramolecular conjugate displacement (ICD). This reaction involves intramolecular addition of a carbanion, which is stabilized by at least one electron-withdrawing group, to a Michael acceptor which has a leaving group in an allylic position. The process formally resembles a combination of Michael addition and SN2′ displacement. The overall result is formation of a ring with loss of the allylic leaving group and shift of the original double bond to a new location spanning the positions of the electron-withdrawing substituent of the Michael acceptor subunit and the original allylic leaving group. The starting materials are easily prepared by a selenium-based version of the Morita−Baylis−Hillman reaction. The cyclizations are transition metal free and occur under mild conditions, using DBU or Cs2CO3 in MeCN or THF. Acetate is a suitable leaving group and the electron-withdrawing substituent of the Michael acceptor unit can be CO2R, SO2Ph, or CN. Six- and seven-membered rings are formed efficiently, and complex structures, such as those resembling the core of CP-225,917, are easily assembled. The products of these ICD reactions are themselves classical Michael acceptors. A range of mechanisms probably operates, depending on the structure of the starting material and the reaction conditions, but conclusive evidence for a stepwise mechanism was obtained in a suitably biased case, while other observations are compatible with a concerted process or a stepwise path involving a short-lived carbanion that evades capture by a proton source. %I ACS Publications