derivatives, respectively, with chemical yields which varied between 72% and 88%. On the other hand, enantiomerically enriched enynes derived from homoallyl and homopropargyl alcohols gave the corresponding opticallyactive dihydropyrans with conjugated diene units with chemical yields between 70% and 80%. A subsequent Diels–Alder reaction of the dihydropyran derivatives with a diene unit with tetracyanoethylene
Stereoselective synthesis of optically active cyclopenta[c]pyrans and cyclopenta[c]furans by the intramolecular Pauson–Khand reaction
作者:Serdar Sezer、Ertan Şahin、Cihangir Tanyeli
DOI:10.1016/j.tetasy.2010.02.016
日期:2010.3
An intramolecular Pauson–Khand reaction of enynes derived from homoallyl, homopropargyl, and allyl alcohols is described. 2-Heteroaryl-substituted homoallyl, homopropargyl, and allyl alcohols are easily and efficiently resolved through enzymatic resolution in high ee (91–99%) and with a known stereochemistry. Each enantiomerically enriched enyne derived from homoallyl and homopropargyl alcohols affords
描述了由高烯丙基,高炔丙基和烯丙醇衍生的烯炔的分子内Pauson-Khand反应。2-杂芳基取代的均烯丙基,高炔丙基和烯丙醇可以通过高ee(91-99%)的酶解和已知的立体化学方法轻松高效地拆分。从高烯丙基和高炔丙基醇,得到构象最稳定的非对映体环戊二烯并[导出的各对映体富集的烯炔Ç ]吡喃环系统作为唯一的产物,而由烯丙基醇得到非对映体衍生的对映体富集烯炔顺:反式的环戊二烯的混合物[ C ^ ]呋喃铃声系统。
Enantioselective Addition of Allyltin Reagents to Amino Aldehydes Catalyzed with Bis(oxazolinyl)phenylrhodium(III) Aqua Complexes
Bis(oxazolinyl)phenylrhodium(III) aqua complexes, (Phebox)RhX2(H2O) [X = Cl, Br], were found to be efficient Lewis acid catalysts for the enantioselective addition of allyl- and methallyltributyltin reagents to amino aldehydes. The reactions proceed smoothly in the presence of 5–10 mol % of (Phebox)RhX2(H2O) complex at ambient temperature to give the corresponding amino alcohols with modest to good enantioselectivity (up to 94% ee).
The intramolecular Pauson-Khand and ring closing metathesis (RCM) reactions of nitrogen containing chiral enynes and dienes are described. The enyne and diene systems comprised of N-propargylated and N-allylated units are constructed on chiral homoallylic or homopropargylic alcohol backbones, respectively, via S(N)2 and/or modified Mitsunobu reactions. The racemic homoallylic and homopropargylic alcohol derivatives were successfully resolved in high ee (93-99%) by applying chemoenzymatic methods using various lipases such as PS-C II, Lipozyme, and CAL-B. Each enantiomerically enriched enyne afforded the most conformationally stable diastereomeric cyclopenta[c]pyridine ring system as the sole product, whereas enantiomerically enriched dienes gave tetrahydropyridine derivatives as a result of intramolecular Pauson-Khand and RCM reactions, respectively. (C) 2012 Elsevier Ltd. All rights reserved.