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Coupling Reaction of Highly Reactive Borates and Substrates with sterichindrance

高反应性硼酸盐与底物的偶联反应

基本信息

批准号：
10650843
负责人：
KOBAYASHI Yuichi
金额：
$ 2.05万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

Recently, we have developed a new type of coupling reagent that allows participation of secondary allylic esters as substrates, thus indicating a high reactivity of the reagents. In this project, we have investigated coupling reaction of these reagents and substrates which have not been investigated due to steric hinderance, and the fruitful results are presented below.(1) Coupling reaction of 8-acetoxy-octalone-Δ^<1(9)>-2 and phenylborates in the presence of a nickel catalyst proceeded stereo- and regioselectively to afford 8-phenyloctalone-Δ^<1(9)>-2 in good yield. Interestingly, the observed stereochemistry is independent of that of the starting allylic substrate. This outcome is not consistent with the well-established mechanism, and we are proposing another one in which the nickel enolates play a central role.(2) Coupling reaction of cyclohexenyl acetates proceeds through the π-allylnickel species which possesses a symmetrical plane and hence presence of a chiral center in a reage … More nt is expected to provide a bias for the regioselectivity. This possibility was examined with arylborates with a chiral substituent at the ortho position to result in a production of one diastereomer highly selectively.(3) Although cis 1-bromoalkenes with a silyloxy substituent at 3-position is less reactive substrates toward the coupling reaction due to the steric hindrance, alkenylborates was found to furnish coupling products efficiently. The reaction was successfully applied in a total synthesis of 10,11-dihydroleukotriene B_4 and the related molecules.(4) With the above reaction, determination of the stereochemistry of natural korormicin was investigated. In practice, possible four diastereoisomers were synthesized stereoselectively by using this coupling reaction, and comparison of their specific rotations with that of the natural one revealed that the (5S,3'R,9'S,10'R)-isomer is unambiguously to be the natural korormicin.(5) Aldol reaction at the α dash position of γ-alkeny-α, β-unsaturated cyclopentenones, easily prepared from the coupling product of 4-cyclopentene-1,3-diol and borates, is investigated and applied to synthesis of Δ^7-PGA_1 methy ester. Less

最近，我们开发了一种新型的偶联试剂，允许二级烯丙基酯作为底物参与，从而表明试剂的高反应活性。在这个项目中，我们研究了由于位阻而没有研究的这些试剂和底物的偶联反应，并给出了丰硕的结果。(1)在镍催化剂的作用下，8-乙酰氧基辛烷酮-Δ^<1(9)>-2与苯硼酸盐进行了立体选择性和区域选择性的偶联反应，得到了产率较高的8-苯基辛烷酮-Δ^<1(9)>-2。有趣的是，观察到的立体化学与起始的烯丙基底物无关。这一结果与已建立的机制不一致，我们提出了另一种镍烯醇化物发挥核心作用的机制。(2)醋酸环己烯酯的偶联反应是通过π-烯丙基镍进行的，该π-烯丙基镍具有对称的平面，因此在反应过程中存在一个手性中心。用手性取代基的芳基硼酸盐进行了这种可能性的检验，结果是高选择性地产生了一种非对映体。(3)由于空间位阻的存在，3位硅氧基取代的顺式1-溴代烯烃在偶联反应中反应较弱，而硼酸烯基酯则是偶联产物的有效载体。该反应成功地合成了10,11-二氢白三烯B_4及其相关分子。(4)利用上述反应，研究了天然科罗米星的立体化学性质。在实际应用中，利用该偶联反应立体选择性地合成了四种可能的非对映异构体，并将其与天然异构体的旋光度进行了比较，结果表明(5S,3'R,9'S,10'R)-异构体无疑是天然的科罗米星。(5)研究了4-环戊烯-1,3-二醇与硼酸盐偶联产物易制得的γ-烯-α， β-不饱和环戊烯酮在α横线位置的醛醇反应，并将其应用于Δ^7-PGA_1甲酯的合成。少