Diastereoselection during 1,2-Addition of the Allylindium Reagent to alpha-Thia and alpha-Amino Aldehydes in Aqueous and Organic Solvents.
Diastereoselection during 1,2-Addition of the Allylindium Reagent to alpha-Thia and alpha-Amino Aldehydes in Aqueous and Organic Solvents.
复制标题
在水和有机溶剂中将烯丙基试剂 1,2-加成到 α-硫杂醛和 α-氨基醛中时的非对映选择。
DOI：
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发表时间：
1997
影响因子：
3.6
通讯作者：
W. Schomer
中科院分区：
文献类型：
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作者：
L. Paquette;T. Mitzel;M. Isaac;C. Crasto;W. Schomer
研究了丙烯基溴与α-硫辛酸(PHS和MES)、双取代α-氨基(Bn(2)N，Me(2)N，异吲哚)和保护的α-氨基醛(Ac和Boc)在水中的铟促进反应的立体化学。涉及硫衍生物的反应是最小的非对映选择性，表明烯丙基试剂不亲硫。没有观察到络合作用，在取代基的空间控制下，通过Felkin-Ahn过渡态实现了人面识别。加纳醛也是非对映选择性的。有趣的是，N-乙酰甘露糖胺对络合控制非常敏感，当在0.5MNH(4)Cl溶液中反应时，能够产生90%的合成β-氨基醇。虽然α-二苄氨基太大而不能进入络合，但α-二甲氨基不是这样，可能会导致高水平的合成非对映异构体(99%)。其他邻近取代基的大小确实会影响这些体系中的pi-Faces分辨，并会相应地侵蚀立体选择性。
The stereochemistry of the indium-promoted reaction of allyl bromide with alpha-thia (PhS and MeS), disubstituted alpha-amino (Bn(2)N, Me(2)N, isoindolyl), and protected alpha-amino aldehydes (Ac and Boc) in water has been evaluated. The reactions involving the sulfur derivatives are minimally diastereoselective, indicating that the allylindium reagent is not thiophilic. Chelation is not observed and pi-facial discrimination is achieved via Felkin-Ahn transition states under the steric control of the substituents. The Garner aldehyde is also anti-diastereoselective. Interestingly, N-acetylmannosamine is appreciably responsive to chelation control and is capable of generating 90% of the syn beta-amino alcohol when reacted in a 0.5 M NH(4)Cl solution. While the alpha-dibenzylamino substituent is too bulky to enter into complexation, the alpha-dimethylamino group is not and can lead to high levels (99%) of syn diastereomer. The size of other neighboring substituents does have an impact on pi-facial discrimination in these systems and can erode the stereoselectivity accordingly.