Stereoselective synthesis of musclides A1, A2 and B
摘要:
An expedient method for the stereoselective preparation of musclide A1, A2 and B, cardiotonic-potentiating principles from musk, has been achieved. The key step is the addition of the O-benzyl ethers of prop-2-yn-1-ol and (R)-but-3-yn-2-ol to aldehydes mediated by zinc triflate, Et3N, and (+)- or (-)-N-methylephedrine. In some cases, the partial reduction of the resulting alkynols to Z-olefins has allowed us to remove the minor stereoisomer easily by chromatography to afford highly stereoenriched precursors of musclides. (C) 2003 Elsevier Science Ltd. All rights reserved.
disclose here that N-alkenoxypyridinium salts, generated readily upon gold-catalyzed additions of protonated pyridine N-oxide to C-C triple bonds of unactivated terminal alkynes, display versatile enolate umpolung chemistry upon heating and react with tethered arene nucleophiles in an SN2' manner. In a synthetically efficient one-pot, two-step process, this chemistry enables expedient preparation of valuable
与烯醇化物对应物相比,烯醇化物 umpolung 反应性为构建普遍存在的羰基化合物提供了有价值且可能独特的替代方案。我们在此公开了 N-链烯氧基吡啶鎓盐,在金催化下将质子化吡啶 N-氧化物与未活化末端炔烃的 CC 三键加成后很容易生成,在加热时显示出多功能的烯醇化极性化学,并以 SN2' 方式与系链芳烃亲核试剂反应。在合成高效的一锅两步法中,这种化学反应能够方便地从易于获得的芳基取代的线性炔烃中方便地制备有价值的苯并稠合七元/八元环酮,包括 O-/N-杂环酮基材。反应收率可达87%。
A convenient scalable one-pot conversion of esters and Weinreb amides to terminal alkynes
作者:Hamilton D. Dickson、Stephon C. Smith、Kevin W. Hinkle
DOI:10.1016/j.tetlet.2004.05.139
日期:2004.7
Esters and amides undergo reduction to the corresponding aldehydes using DIBAL-H followed by same pot conversion to terminal alkynes utilizing the Bestmann-Ohira reagent in good to excellent yields. Additionally chiral nonracemic Substrates undergo this transformation with complete preservation of stereochemical integrity. (C) 2004 Elsevier Ltd. All rights reserved.