Efficient control of the diastereoselectivity and regioselectivity in the singlet-oxygen ene reaction of chiral oxazolidine-substituted alkenes by a remote urea NH functionality:: Comparison with dimethyldioxirane and m-chloroperbenzoic acid epoxidations
Efficient control of the diastereoselectivity and regioselectivity in the singlet-oxygen ene reaction of chiral oxazolidine-substituted alkenes by a remote urea NH functionality:: Comparison with dimethyldioxirane and m-chloroperbenzoic acid epoxidations
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DOI：
10.1021/ja010463k
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发表时间：
2001-08-01
影响因子：
15
通讯作者：
Schambony, SB
中科院分区：
文献类型：
--
作者：
Adam, W;Peters, K;Schambony, SB
手性恶唑烷取代的烯烃的单重态氧烯反应和DMI环氧化反应，具有自由的尿素NH官能团和构象固定的双键，以高的类非对映选择性(高达>；95：5)进行；O-1(2)烯反应也发现了高的区域选择性。通过甲基化封顶自由NH官能团，消除了这两种氧化剂的类似选择性，并显著降低了烯反应中的区域选择性。这些数据证明了远程尿素NH官能团和有利于对C-C双键进行类似攻击的氧化剂之间的有效氢键。对于O-1(2)，激基络合物中的氢键导致从烷基顺式到直接尿素官能团的优先抽氢。
The singlet-oxygen ene reaction and the epoxidation by DMI) of chiral oxazolidine-substituted alkenes, equipped with a free urea NH functionality and a conformationally fixed double bond, proceed in high like diastereoselectivity (up to >95:5); also a high regioselectivity was found for the O-1(2) ene reaction. Capping of the free NH functionality by, methylation erases this like selectivity for both oxidants and significantly reduces the regioselectivity in the ene reaction. These data demonstrate effective hydrogen bonding between the remote urea NH functionality and the oxidant that favors the like attack on the C-C double bond. For O-1(2), the hydrogen bonding in the exciplex results in preferred hydrogen abstraction from the alkyl group cis to the directing urea functionality.