Pyrroline derivatives, asymmetric

The reaction of alkenylcarbene complexes and imines in the presence of a Lewis acid generates pyrroline derivatives as a result of a [3C+2S] cyclisation process [76]. This reaction has been extended to an asymmetric version by the use of chiral alkenylcarbene complexes derived from several chiral alcohols. However, the best results are found when (-)-8-phenylmenthol-derived complexes are used and catalytic amounts of Sn(OTf)2 are added to the reaction. In these conditions high levels of trans/cis selectivity are achieved and the hydrolysis of the major tram diastereoisomers allows the preparation of optically pure 2,5-disubstituted-3-pyrrolidinone derivatives (Scheme 29). 

The phosphine-phosphite BINAPHOS ligand was first used in the Rh-catalyzed asymmetric hydroformylation of heterocyclic olefins such as 2,5-dihydrofuran, 3-pyrroline derivatives, and 4,7-dihydro-1,3-dioxepin derivatives. It provided the optically active aldehydes as single products with enantioselectivity between 64-76% ee. In the hydroformylation of 2,5-di-... 

The reaction of Fischer alkenyl carbene complexes 101 with imines 102 in the presence of a Lewis acid generates pyrroline derivatives 105 as a result of a formal [3+2] cycloaddition via metallacyclic intermediates 103 (Scheme 5.21) [32]. The intermediates 103 are supposed to be formed through a metalla-Diels-Alder reaction. High asymmetric induction is observed in the reaction of chiral alkenyl carbene complexes 101 derived from (—)-8-phenyl-menthol. The major isomer of the trans products 104 can be... 

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