4 + 1 Radical annulations with isonitriles: a simple route to cyclopenta-fused quinolines
作者:Dennis P. Curran、Hui Liu
DOI:10.1021/ja00006a033
日期:1991.3
this first example of a 4+1 radical annulation includes the following: (1) radical addition to an isonitrile, (2) cyclization of the resulting imidoyl radical to the alkyne, (3) addition of the so-formed vinyl radical to the aromatic ring, and (4) rearomatization. When substituted isonitriles (p-F p-OMe, m-F) are employed, the major unrearranged products are accompanied by 7-30% or rearranged products
1-取代的 5-碘-1-戊炔、5 当量的苯基异氰化物和 1.5 当量的六甲基二锡在 150 o C 的叔丁基苯 (0.01-0.025 M) 中的太阳灯照射产生 9-取代的 2,3-二氢-1H -cyclopenta [b] 喹啉的产率为 36-70%。4+1 自由基环化的第一个例子的机制建议包括以下内容:(1) 自由基加成到异腈,(2) 所得亚胺酰基自由基环化到炔烃上,(3) 加成如此形成的乙烯基芳环上的自由基,和(4)重构化。当使用取代的异腈(pF p-OMe,mF)时,主要的未重排产物伴随有 7-30% 或重排产物。提出的中间体的独立生成表明,重排产物是通过乙烯基自由基的初始闭合形成五元环而产生的,
Tandem Pd-Catalyzed Cyclization/Coupling of Non-Terminal Acetylenic Activated Methylenes with (Hetero)Aryl Bromides
作者:Aleksandra Błocka、Wojciech Chaładaj
DOI:10.3390/molecules27030630
日期:——
methylene compounds to internal alkynes followed by coupling with aryl and heteroaryl bromides. Highly substituted vinylidenecyclopentanes were obtained with good yields, complete selectivity, and excellent functional group tolerance. A plausible mechanism, supported by DFT calculations, involves the oxidative addition of bromoarene to Pd(0), followed by cyclization and reductive elimination. The excellent
Tungsten(0)‐ and rhenium(I)‐catalyzed reactions of acetylenic dienolsilylethers based on the concept of geminal carbo‐functionalization of alkynes are reported. Treatment of 3‐siloxy‐1,3‐diene‐7‐ynes with catalytic amounts of [W(CO)6] or [ReCl(CO)5] under photoirradiation conditions gives synthetically useful bicyclo[3.3.0]octane derivatives in good yields. Extremely high catalytic activity is noted
enantioselective catalyticasymmetric conjugate addition to forge the challenging all‐carbon quaternary stereogenic center that was used to induce the formations of all other chiral centers of the molecule; and (3) as a C1N1 building block to form the 3‐azabicyclo[3.3.1]nonane framework. The realization of this strategy relied on the development of a novel organocatalytic asymmetric conjugate addition of nitromethane
我们描述了总合成盐素A的全部细节,该盐是一种大环天然产物,被建议源自常见的生物合成中间体,即苦味素A。合成路线的核心是战略性地使用硝基甲烷进行多种用途:(1)作为一种合成油氨基甲基的替代物;(2)作为高度对映选择性催化不对称共轭物的理想亲核试剂,以锻造具有挑战性的全碳四元立体异构中心,该中心被用来诱导分子的所有其他手性中心的形成;和(3)作为C 1 N 1构建单元以形成3-氮杂双环[3.3.1]壬烷框架。该策略的实现依赖于新的有机催化不对称的硝基甲烷共轭加成反应,将硝基甲烷添加到3-烯基环己二-2-烯酮中,以及第一个由Pd促进的硫代氨基甲酸酯部分分子内偶联到电子缺陷的烯(烯酮)上。形成3-氮杂双环[3,3,1]壬烷核。该合成还具有烯酮与醛的SmI 2介导的分子间还原偶联,闭环的烯烃和炔烃复分解反应以构建两个氮杂大环,以及烯醇史无前例的直接转化为烯酮。
A Conia‐Ene‐Type Cyclization under Basic Conditions Enables an Efficient Synthesis of (−)‐Lycoposerramine R
作者:Felix W. W. Hartrampf、Takayuki Furukawa、Dirk Trauner
DOI:10.1002/anie.201610021
日期:2017.1.16
An enantioselective total synthesis of the Lycopodium alkaloid lycoposerramine R is presented. It relies on a base‐mediated cyclization that resembles the Conia‐ene reaction of ynones and gold‐catalyzed variants thereof. Thus, hydrindanones and other functionalized ring systems bearing an exocyclic alkene can be rapidly accessed at room temperature without noble metal catalysis or substrate preactivation