Only chiral anions do the job! Optically active gold complexes derived from substituted binol hydrogen phosphate catalyze the desymmetrizing cyclization of 1,4-diynamides. This reaction provides access to synthetically useful, chiral methylene pyrrolidines with an all-carbon-substituted quaternary stereocenter.

A general synthetic access to 3,3-disubstituted 1,4-diynes bearing a quaternary carbon center from acetylacetone was developed. The compounds were cyclized to the corresponding enol ethers by cationic gold complexes. The reactions occur in complete exo-selectivity in contrast to compounds incorporating an alkoxy substituent in the 3-position. A mechanistic rationale for this reversal of selectivity is provided.

Zone Fayoum, 63514 (¾gypten) [**] Diese Arbeit wurde großzügig durch die DFG im Rahmen des Emmy-Noether-Programms gefçrdert (CZ 183/1). A.K.M. ist dankbar für ein DAAD-Promotionsstipendium. Dr. Roman Rüttinger wird gedankt für seinen experimentellen Beitrag zur Anwendung chiraler Phosphanliganden (Tabelle 1). Hintergrundinformationen zu diesem Beitrag sind im WWW unter http://dx.

Reversal of Selectivity in Gold-Catalyzed Cyclizations of 3,3-Disubstituted 1,4-Di-ynes. -Diyne substrates bearing exclusively alkyl or aryl substituents are prepared starting from acetylacetone via the known alcohols (I) following a new synthetic pathway which includes allylation. The cyclization of these compounds occurs with complete exo-selectivity to give the corresponding cyclic enol ethers (VII) or (VIII). This is in contrast to substrates bearing an alkoxy substituent at the 3-position which form seven-membered heterocycles. -(RUETTINGER, R.; LEUTZOW, J.; WILSDORF, M.; WILCKENS, K.; CZEKELIUS*, C.; Org. Lett. 13 (2011) 2, 224-227, http://dx.

Anion-Induced Enantioselective Cyclization of Diynamides to Pyrrolidines Catalyzed by Cationic Gold Complexes. -A new method is presented which affords optically active methylene pyrrolidines via cycloisomerization of 1,4-diynamides under optimized conditions. -(MOURAD, A. K.; LEUTZOW, J.; CZEKELIUS*, C.; Angew.