Organocatalytic Asymmetric Formal [3 + 2] Cycloaddition with in Situ-Generated <i>N</i>-Carbamoyl Nitrones
作者:Claudio Gioia、Francesco Fini、Andrea Mazzanti、Luca Bernardi、Alfredo Ricci
DOI:10.1021/ja902458m
日期:2009.7.22
A novel organocatalytic formal [3 + 2] cycloaddition reaction with in situ generation of N-carbamoyl nitrones is presented. For the first time, N-Boc- and N-Cbz-protected isoxazolidines have been directly obtained as single diastereoisomers in generally high yields and enantiomeric excesses using mild reaction conditions and inexpensive, readily available Cinchona alkaloid quaternary ammonium salts
提出了一种新的有机催化形式 [3 + 2] 环加成反应,原位生成 N-氨基甲酰基硝酮。首次使用温和的反应条件和廉价、易得的金鸡纳生物碱季铵盐作为催化剂,直接以单一非对映异构体形式获得 N-Boc 和 N-Cbz 保护的异恶唑烷,收率通常很高,对映体过量。产品的合成操作提供了非常有价值的构建块,例如游离异恶唑烷、N-Boc-1,3-氨基醇和游离 δ-内酰胺。这份报告代表了在不对称催化中使用 N-氨基甲酰基硝酮作为缺电子 1,3-偶极子和戊二酸作为新的偶极子的开创性工作。