Asymmetric thio-claisen rearrangement induced by an enantiopure alkylsulfinyl group. Unusual preference for a boat transition state in the acyclic series
Asymmetric thio-claisen rearrangement induced by an enantiopure alkylsulfinyl group. Unusual preference for a boat transition state in the acyclic series
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DOI：
10.1021/jo015956m
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发表时间：
2001-11-16
影响因子：
3.6
通讯作者：
Averbuch-Pouchot, MT
中科院分区：
文献类型：
--
作者：
Nowaczyk, S;Alayrac, C;Averbuch-Pouchot, MT
烯基氨基硫缩醛2a-c和5a-b，含对映纯乙烯基烷基亚砜基。以(R)-2-环己基亚砜- n， n -二甲基乙烷乙酰胺1为原料制备取代基，完全控制其双键的几何形状。它们在THF回流加热后进行Claisen重排，得到α -亚砜酰γ -不饱和硫酰胺3a-c和6a-b。在所有底物中，亚砜基的不对称诱导都很好。用x射线晶体学分析或化学对比法确定了硫酰胺3a-c和6a-b的绝对构型。用电子模型解释了[3,3]符号位转置的立体化学过程。有趣的是，(ZE)-肉桂基底物5b的Claisen重排被证明是通过船型过渡态而不是椅子过渡态进行的；这样的偏好在非循环系统中是很不寻常的。
Ketene aminothioacetals 2a-c and 5a-b bearing an enantiopure vinylic alkylsulfinyl. substituent were readily prepared from (R)-2-cyclohexylsulfinyl-N,N-dimethylethanethioamide 1 with full control of the geometry of their double bonds. They underwent a Claisen rearrangement upon heating at THF reflux to afford alpha -sulfinyl gamma -unsaturated thioamides 3a-c and 6a-b. With all substrates the asymmetric induction of the sulfinyl group was excellent. The determination of the absolute configurations of thioamides 3a-c and 6a-b was achieved either by X-ray crystallographic analysis or by chemical correlation. The stereochemical course of this [3,3] sigmatropic transposition was explained by an electronic model. Interestingly the Claisen rearrangement of the (ZE)-cinnamyl substrates 5b was shown to proceed through a boat transition state rather than a chair transition state; such a preference is quite unusual for acyclic systems.