Asymmetric Nitrocyclopropanation of alpha-Substituted alpha,beta-Enals Catalyzed by Diphenylprolinol Silyl Ether for the Construction of All-Carbon Quaternary Stereogenic Centers

作者：Hayashi Yujiro^*; Yamazaki Tatsuya; Nakanishi Yuki; Ono Tsuyoshi; Taniguchi Tohru; Monde Kenji; Uchimaru Tadafumi

来源：European Journal of Organic Chemistry, 2015, 2015(26): 5747-5754.

DOI：10.1002/ejoc.201500838

• Organocatalysis
• Asymmetric synthesis
• Small ring systems
• Cyclopropanation
• Chirality

The diphenylprolinol silyl ether mediated asymmetric nitrocyclopropanation of -substituted ,-unsaturated aldehydes with bromonitromethane, followed by base-promoted isomerization was found to afford trans-nitrocyclopropanecarbaldehydes with all-carbon quaternary stereogenic centers with excellent diastereo- and enantioselectivities. DFT calculations indicated that the s-trans conformer of the iminium ion intermediate is more stable than the s-cis conformer. In addition, nucleophilic attack of the bromonitromethane anion to the iminium ion intermediate was calculated to occur preferentially from the opposite side of the bulky substituents of the pyrrolidine iminium intermediate.

• 出版日期2015-9