Synthesis of [1,2-a]-fused tricyclic dihydroquinolines by palladium-catalyzed intramolecular C–N cross-coupling of polarized heterocyclic enamines
作者:Břetislav Brož、Zdeňka Růžičková、Petr Šimůnek
DOI:10.3998/ark.5550190.p009.723
日期:——
A simple methodology for [1,2-a]-fusedtricyclicdihydroquinolines is established. The key step of the methodology is an intramolecular Buchwald-Hartwig amination reaction of suitable halogenated (both bromo and chloro) cyclic enaminoketones, enaminoesters and enaminonitriles with various ring size (from fiveto seven-membered). Optimal reaction conditions (palladium source, base, ligand) depend on
reaction conditions. However, this catalytic system exhibited much lower activity in the hydrogenation of substituted phenols. Pyridine was easily hydrogenated under mild conditions and interestingly, the hydrogenation of 4-methyl and 4-trifluoromethylpyridine resulted slower than that of 2-methylpyridine. The hydrogenation of 1-(pyridin-2-yl)propan-2-one provided the β-enaminone 13a in high yield as a consequence
新的Rh-的NP稳定的N-杂环卡宾(NHC)通过的[Rh(η分解合成3 -C 3 H ^ 5)3 1 H下2气氛和完全表征。还进行了使用同位素标记的配体通过FT-IR和NMR光谱进行的表面研究。相对湿度0.2NP是还原各种芳族底物的活性催化剂。在苯酚的还原中,取决于反应条件,获得了对环己酮或环己醇的高选择性。但是,该催化体系在取代酚的氢化中表现出低得多的活性。吡啶在温和条件下容易氢化,有趣的是,4-甲基和4-三氟甲基吡啶的氢化反应比2-甲基吡啶的氢化反应慢。1-(吡啶-2-基)丙-2-酮的氢化提供了β-烯胺酮13a吡啶环部分还原,然后异构化的结果是高收率。通过调节反应条件,可以将喹啉部分氢化为1,2,3,4-四氢喹啉或完全还原为十氢喹啉。
A new bicyclic oxazaborines with a bridged nitrogen atom, their thermic rearrangement and fluorescence properties
Cyclic beta-enaminones bearing secondary amino group react with 4-substituted benzenediazonium tetraphenylborates in dichloromethane to form substituted bicyclic [1,3,2 lambda(4)] oxazaborines The oxazaborines rearrange, on heating to 200 degrees C in the absence of solvent or in DMF or DMSO, to isomeric 2H-[1,2,4,3 lambda(4)] triazaborines. Previously prepared [1,3,2 lambda(4)] oxazaborines derived from acyclic beta-enaminones bearing secondary amino group either did not undergo the rearrangement or with a lot of difficulties and with negligible yield. The fluorescence behaviour of the prepared triazaborines was observed. These compounds fluoresce in 2-methyltetrahydrofurane and in solid state under low temperatures. (C) 2011 Elsevier B.V. All rights reserved.
A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates
substituents was easily synthesized. A mechanism of the formation of the pyridazinium salts is suggested. A partial drawback is the possibility of the formation of a mixture of products when using a different diazonium salt in each step due to a reversibility of the azo coupling. This can be suppressed by using a more reactive diazonium salt before a less reactive one.