ortho-Lithiation of S-tert-butyl-S-phenylsulfoximines. New route to enantiopure sulfinamides via a de-tert-butylation reaction
摘要:
The sulfoximine group proved to be an excellent ortho-directing group in lithiation reactions. Several electrophiles were used to afford the corresponding ortho-functionalized aryl sulfoximines in good yields. The use of prochiral electrophiles lead to modest to good diastereoselectivities up to 95%. During this study, we observed a side reaction due to a S-de-tert-butylation. After optimization of this S-de-tert-butylation reaction, the corresponding enantiopure sulfinamides could be obtained in good yields. (c) 2005 Elsevier Ltd. All rights reserved.
The readily available S-(tert-butyl)-N-(trimethylsilyl)-S-phenylsulfoximine was prepared from S-methyl-N(trimethylsilyl)-S-phenylsulfoximine via lithiation-methylation sequences. The reaction with n-butyllithium in THF at -78 degrees C afforded the corresponding ortho-lithiated species which could be trapped with different electrophiles in good yields. Addition of benzaldehyde proceeded with a modest diastereoselectivity (de=52%). (C) 1999 Published by Elsevier Science Ltd. All rights reserved.
ortho-Lithiation of S-tert-butyl-S-phenylsulfoximines. New route to enantiopure sulfinamides via a de-tert-butylation reaction
The sulfoximine group proved to be an excellent ortho-directing group in lithiation reactions. Several electrophiles were used to afford the corresponding ortho-functionalized aryl sulfoximines in good yields. The use of prochiral electrophiles lead to modest to good diastereoselectivities up to 95%. During this study, we observed a side reaction due to a S-de-tert-butylation. After optimization of this S-de-tert-butylation reaction, the corresponding enantiopure sulfinamides could be obtained in good yields. (c) 2005 Elsevier Ltd. All rights reserved.