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【You Huang Group】Bifunctional-Phosphine-Catalyzed Sequential Annulations of Allenoates and Ketimines: Construction of Functionalized Poly-heterocycle Rings

Source：SKLEOC   Date：2016/10/11

 

 
Sequential annulations are one of the most powerful methods for preparing structurally divergent polycyclic systems. Over the last decades, many chemists have devoted efforts to develop a highly efficient strategy to construct these polycyclic skeletons, which are widely found in natural products with significant biological properties.In this field, the success is predominant at transition-metal-catalyzed intramolecular annulation reactions.Nevertheless, such transition-metal-catalyzed reactions always rely on the use of non-commercially available or expensive ligands and has limited substrate scope, which severely restrict application in organic and pharmaceutical synthesis. Thus, developing a novel way to build the polycyclic systems in one step from readily available starting materials remains necessary.
Prof. Huang' group developed a series of phosphine-catalyzed sequential annulation reactions to build the bicyclic compounds by intermolecular way.No examples of asymmetric annulation reaction have been developed to build polycyclic compounds by intermolecular sequential annulations to date. This is because of the existence of some challenges: 1) Complex products are often formed in these reactions; 2) sequential chiral centers increase the difficulty in steric-control; and 3) multiple diastereoisomers are often obtained in these reactions.
Recently, Prof. Huang reported a highly stereoselective sequential annulation reaction between γ-substituted allenoates and ketimines. By using bifunctional N-acyl aminophosphine catalysts, poly-heterocycle rings were obtained with high stereocontrol in good to excellent yields. Theyare first to report an asymmetrical intermolecular method to obtain poly-heterocyclic products by using chiral phosphine catalyst and the desired products gave four-contiguous stereogenic centers (one quaternary and three tertiary carbon), and only one isomer was obtained in all reactions.

Link: http://onlinelibrary.wiley.com/doi/10.1002/anie.201605189/full .

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