The Studies On Allylic Sulfonium Ylide Cyclization Reaction

Much attention has been paid to the highly stereoselective synthesis of allylic small ring compounds. Of the synthetic methods developed, ylide-initiated Michael addition/cyclization reaction represents a convenient and useful method. This thesis mainly focused on the tandem Michael addition/ylide epoxidation reaction, the sulfur ylide cyclopropanation and sulfur ylide-mediated aziridination.In the first part, a tandem Michale-addition/epoxidation reaction of camphor-derived sulfonium salt 2a withβ-aryl, alkyl, and H substitutedα,β-unsaturated ketones was developed. The reaction proceeded smoothly to afford optically active cyclohexene epoxide derivatives with high enantiomeric excesses in good yields by remote control of enantioselectivity via chiral sulfur ylides. The absolute structure of cyclohexadiene epoxide 3c was further elucidated by X-ray analysis as (1S,4S,6S)-3c. We also proposed a mechanism and synthesis the intermediate sulfonium salt 20 to account for the observed results of the asymmetric ylide-initiated reaction. Under the different conditions, we also can controllable synthesis 1,3-disubstituted-2-vinylcyclopropanes with high diastereoselectivities(> 25/1) and enantioselectivities(97-99%) using camphor-derived sulfonium salt 2a. In all cases studied, no cyclohexadiene epoxide products was observed. The absolute configuration of cyclopropane 4a was further elucidated by chemical transformation as (1S,2S,3R)-4a. On the basis of these results, together with the absolute configuration of the product, stereochemical model was developed to explain the stereochemistry which is consistent with the experimental results.In the second part, we developed a one-pot protocol to construct cis-vinylaziridine by combining allylic ylide aziridination with Pd(0)-catalyzed isomerization reaction of vinylaziridine. Following this protocol, a series of cis-trisubstituted vinylaziridines containing a quaternary carbon center were synthesized with exclusive cis-selectivity (cis/trans > 99/1) in moderate to good yields starting with allylic sulfur ylide and cyclic ketimines. We also studied the asymmetric version of this reacton and optically active cis-trisubstituted vinylaziridines could be obtained with high diastereoselectivities and excellent enantiomeric excesses in good yields.