ASYMMETRIC INDUCTION IN INTRAMOLECULAR ENE REACTIONS OF CHIRAL 1,7-DIENES - A DIASTEREOSELECTIVE AND ENANTIOSELECTIVE SYNTHESIS OF SUBSTITUTED CYCLOHEXANES
ASYMMETRIC INDUCTION IN INTRAMOLECULAR ENE REACTIONS OF CHIRAL 1,7-DIENES - A DIASTEREOSELECTIVE AND ENANTIOSELECTIVE SYNTHESIS OF SUBSTITUTED CYCLOHEXANES
复制标题
DOI：
10.1021/jo00274a031
复制
发表时间：
1989-06-23
影响因子：
3.6
通讯作者：
RUTHER, M
中科院分区：
文献类型：
--
作者：
TIETZE, LF;BEIFUSS, U;RUTHER, M
研究了亲烯体上两个吸电子基团活化的手性1，7-二烯9在分子内热催化和刘易斯酸催化的烯反应中的不对称诱导。从分子内烯，连续烯，和杂狄尔斯-桤木反应的环加合物的特征在于，并确定所获得的非对映异构体的比例。香茅醛（8）与无环1，3-二羰基及类似化合物7的Knoevenagel缩合反应得到相应的1，7-二烯9，后者在热条件下与ZnBr 2环化得到反式取代烯产物15和16，杂-Diels-桤木产物17和18，以及顺序烯产物19和20，取决于末端的吸电子基团。丙二酸酯9a-c的衍生物只得到15和16，而乙酰丙酮9 f的衍生物得到17 b和18 b。刘易斯酸催化反应9 g/9 h主要得到19 b。非对映体对15/16、17/18和19/20的比例（在180 ℃下de值= 74.0-84.0%，在25 ℃下de值= 82.0-95.0%）由在所提出的椅状过渡态中C-5处的甲基的赤道取向的偏好和亲烯体中吸电子基团的空间需求决定。烯加合物作为十氢萘的前体在天然产物的合成中具有重要的应用价值，区域和立体选择性的CC键形成反应的发展是有机合成中的一个重要目标。分子内烯反应近年来受到了广泛的关注，并为碳环戊烷和杂环戊烷的形成提供了一种有价值的方法。2，3然而，对于非反应性烯和亲烯体，
The asymmetric induction in intramolecular thermal and Lewis acid catalyzed ene reactions of chiral 1, 7-dienes 9 activated by two electron-withdrawing groups on the enophile is studied. The cycloadducts resulting from intramolecular ene, sequential ene, and hetero-Diels-Alder reactions are characterized and the ratio of the diastereomers obtained is determined. Knoevenagel condensation of citronellal (8) with acyclic 1, 3-dicarbonyl and analogous compounds 7 gave the corresponding 1, 7-dienes 9, which cyclized under thermal conditions and with ZnBr2 to the trans-substituted ene products 15 and 16, the hetero-Diels-Alder products 17 and 18, and the sequential ene products 19 and 20, depending on the electron-withdrawing groups at the terminus. Derivatives of malónate 9a-c led exclusivelyto 15 and 16, whereas those of acetylacetone 9f gave 17b and 18b. Lewis acid catalyzed reaction of9g/9h afforded mainly 19b. The ratio of the diastereomeric pairs 15/16, 17/18, and 19/20 with de values= 74.0-84.0% at 180 C and 82.0-95.0% at 25 C is governed by the preference of an equatorial orientation of the methyl group at C-5 in the proposed chairlike transition state and the steric demand of the electron-withdrawing groups in the enophile. The ene adducts are of value as decalin precursors in the synthesis of natural products.The development of regio-and stereoselective CC bond-forming reactions is a key objective in organic synthesis. Theintramolecular ene reaction has recently re-ceived considerable attention2 3and offers a valuable method for the formation of car bo-and heterocyclic cyclo-pentanes. 2, 3 However, with unreactive enes and enophiles,