Allylation of Exocyclic <i>N</i>-Acyliminium Ions Generated from Chiral <i>N</i>-[1-(Phenylsulfonyl)alkyl]oxazolidin-2-ones
作者:Enrico Marcantoni、Tiziana Mecozzi、Marino Petrini
DOI:10.1021/jo0162888
日期:2002.5.1
N-[1-(Phenylsulfonyl)alkyl]oxazolidin-2-ones are successfully prepared by condensation of the corresponding optically active oxazolidin-2-ones with aldehydes and benzenesulfinic acid. At low temperature, in the presence of titanium tetrachloride, these sulfones are converted into N-acyliminium ions, which react with allyltrimethylsilane with a variable degree of stereoselectivity. The best results
通过将相应的旋光恶唑烷-2-酮与醛和苯亚磺酸缩合,可以成功制备N- [1-(苯磺酰基)烷基]恶唑烷-2-酮。在低温下,在四氯化钛的存在下,这些砜被转化为N-酰亚胺离子,它们与烯丙基三甲基硅烷以可变的立体选择性反应。用(R)-5,5-二甲基-4-苯基恶唑烷丁-2-酮作为手性助剂可获得最佳结果。用锂/氨裂解恶唑烷-2-酮环得到相应的均烯丙基胺,其显示出与通常的空间效应相反的绝对构型。路易斯酸与N-酰基亚胺离子的络合可能是这种不寻常的立体化学结果的原因。