Very high 1,2- and 1,3-asymmetric induction in the reactions of allylic boron compounds with chiral imines.
Very high 1,2- and 1,3-asymmetric induction in the reactions of allylic boron compounds with chiral imines.
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DOI：
10.1021/ja00284a048
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发表时间：
1986-11
影响因子：
15
通讯作者：
Y. Yamamoto;K. Maruyama;T. Komatsu;W. Ito
中科院分区：
文献类型：
--
作者：
Y. Yamamoto;K. Maruyama;T. Komatsu;W. Ito
烯丙基-9-硼双环[3.3. 1]壬烷（烯丙基-9-BBN）与手性亚胺3单独或非常主要地产生Cram异构体4。很高的1，2-不对称诱导是由六元椅状过渡态解释的，在该过渡态中，由于亚胺的立体电子效应（RCH= NR '），亚胺R基团占据轴向位置.烯丙基-9-BBN与手性亚胺11的反应也非常主要地得到Cram异构体12。非常高的1，3-不对称诱导由类似的过渡态（14）解释，其中R '基团和配体L之间的1，2-轴向-赤道相互作用对高手性诱导起重要作用。通过烯丙型9-BBN与R '基团上具有手性助剂的亚氨基酯（27）的反应，实现了氨基酸衍生物的非常高的对映体和非对映体选择性合成。修正的Cram（或Felkin）模型（9或9/）适用于解释1，2-不对称诱导。对于1，3-不对称烯丙基硼化反应，提出了扩展的Cram模型（10），发现无环体系中1，2-和1，3-不对称诱导反应的新方法是现代有机化学中一个迫切关注的问题。1特别是，Cram/反Cram问题一直是长期关注的问题之一。尽管在过去的十年中，人们对醛的Cram/anti-Cram选择性进行了深入的研究，但很少有人试图阐明亚胺的这种选择性。3，4这是相当
The reaction of allyl-9-borabicyclo [3.3. 1] nonane (allyl-9-BBN) with chiral imines 3 produced the Cram isomer 4 either exclusively or very predominantly. The very high 1, 2-asymmetric induction is explained by a six-membered chairlike transition state, in which the imine R group occupies an axial position owing to the stereoelectronic effect of imines (RCH= NR'). The reaction of allyl-9-BBN with the chiral imine 11 also gave the Cram isomer 12 very predominantly. The very high1, 3-asymmetric induction is accounted for by a similar transition state (14), in which the 1, 2-axial-equatorial interaction between the R'groupand the ligand L plays an important role for the high chiral induction. Very high enantio-and diastereoselective synthesis of amino acid derivatives was realized via the reaction of allylic 9-BBN with-imino esters (27) having a chiral auxiliary at the R'group. The modified Cram (or Felkin) model (9 or 9/) is applicable to explain the 1, 2-asymmetric induction. For the 1, 3-asymmetric allylboration, the extended Cram model (10) is proposed.The discovery of new methods for 1, 2-and1, 3-asymmetric induction in acyclic systems has beena pressing concern in modem organic chemistry. 1 Especially, the Cram/anti-Cram problem has been one of the longstanding concerns. Although the Cram/anti-Cram selectivity of aldehydes has been intensely investigated during thelast decade, 2 very few attempts have been made to elucidate such selectivity with imines. 3, 4 It was rather