Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK.
Chem Asian J. 2010 Mar 1;5(3):589-604. doi: 10.1002/asia.200900470.
The acid-promoted cyclizations of a range of N-benzylethanolamines (derived from pseudoephedrine or ephedrine) give the corresponding trans-N(2),3-dimethyl-4-phenyl-1,2,3,4-tetrahydroisoquinolines with high levels of diastereoselectivity and in good yields of isolated product. The cyclizations of the corresponding chromium tricarbonyl complexes are rendered completely stereoselective. Acid-promoted cyclization of N-(3',4'-dimethoxybenzyl)ephedrine and its chromium tricarbonyl complex occur with complementary diastereoselectivities to give trans- and cis-N(2),3-dimethyl-4-phenyl-6,7-dimethoxy-1,2,3,4-tetrahydro-isoquinoline, respectively, in >99:1 d.r. The latter is consistent with a "double inversion" mechanism, which involves neighboring group participation by the chromium tricarbonyl moiety followed by rearomatization to give the corresponding cis-tetrahydroisoquinoline with overall retention of configuration.
一系列 N-苯乙基亚乙醇胺（来源于伪麻黄碱或麻黄碱）在酸促进下环化，得到相应的反式-N(2),3-二甲基-4-苯基-1,2,3,4-四氢异喹啉，具有高水平的非对映选择性和良好的分离产物收率。相应的三羰基铬配合物的环化反应完全具有立体选择性。N-(3',4'-二甲氧基苄基)麻黄碱及其三羰基铬配合物在酸促进下环化，具有互补的非对映选择性，分别以大于 99:1 的 d.r. 得到反式-N(2),3-二甲基-4-苯基-6,7-二甲氧基-1,2,3,4-四氢异喹啉和顺式-N(2),3-二甲基-4-苯基-6,7-二甲氧基-1,2,3,4-四氢异喹啉。后者与“双重反转”机制一致，其中涉及到三羰基铬部分的邻基参与，然后重排得到相应的顺式四氢异喹啉，整体保留构型。
