An efficient and simple method for synthesis of 2,2-disubstituted-2H-chromenes by condensation of a phenol with a 1,1-disubstituted propargyl alcohol using BF3·Et2O as the catalyst

Gram Scale Total Synthesis of 2‐Hydroxy‐3‐methylcarbazole, Pyrano[3,2‐a]carbazole and Prenylcarbazole Alkaloids

“…of boron tribromide in dichloromethane afforded 9‐benzyl‐3‐methyl‐2‐hydroxycarbazole 7b in 89 % yield (Scheme ). Various Lewis acids, such as ethylenediamine diacetate,20a Ti(O i Pr) 4 ,16,20b BF 3 · H 2 O20c and phenylboronic acid20e were then investigated for their ability to promote the reaction of 7b with 3‐methylbut‐2‐enal. The optimum conditions for formation of the six‐membered oxa ring, affording 17 in 90 % isolated yield entailed the use of PhB(OH) 2 (4 equiv.)…”

Ecocatalysis for 2H-chromenes synthesis: an integrated approach for phytomanagement of polluted ecosystems

“…It is important to note that nucleophiles conventionally considered to be insufficiently reactive in this type of reaction can be used here, thanks to ecocatalysis. This is, for example, the case for phenol (Table 2, entry 4) and naphthol (Table 2, entry 5), whose corresponding 2H-chromenes have been accessed in previous reports with toxic or non-eco-friendly catalysts such as rhenium pentacarbonyl chloride (Zeng et al 2011), TiCl 4 (Sartori et al 1979, or BF 3 ·Et 2 O (Madabhushi et al 2012). However, the Eco-Zn-catalyzed reaction with a substrate bearing an electron-withdrawing substituent, poorer in electrons than phenol, such as 3-bromophenol (Table 2, entry 8) gave only traces of the corresponding chromene.…”

Synthesis of Chromans via Domino Reaction of Phenols with Prenyl Bromide Catalyzed by Zinc Chloride

“…在文献中关于苯并吡喃的合成方法已有 很多报道. 较为主要的路线涉及酚与烯类化合物的反 应 [3] , 其中包括: 第一类, 酚与共轭二烯烃的反应, 采用 的 催 化 剂 或 促 进 剂 包 括 酚 铝 [4] 、 AuCl 3 /AgOTf [5] 、 AgOTf [6] 、 AgOTf/t-BuCl [7] 、 Sc(OTf) 3 / 离 子 液 体 [8] 、 Cu(OTf) 2 /PPh 3 [9] 、 阳离子交换树脂 Amberlyst 15 [10] 等; 第 二类, 酚与烯丙醇或烯丙醇酯的反应, 使用 CpMoCl-(CO) 3 [11] 、 (acac) 2 Mo(SbF 6 ) 2 [12] 、 BF 3 •Et 2 O [13] (6) n-Hexane 0.1 45 24 81 4 AlCl 3 (6) n-Hexane 0.1 45 24 89 5 Al(OTf) 3 (6) 8, 158.3, 131.7, 129.2, 121.9, 120.7, 117.2, 75.4, 60.6, 32.6, 27.0, 22.4, 14.5 8, 141.3, 132.9, 128.8, 128.2, 126.8, 126.6, 126.2, 121.2, 117.7, 74.6, 33.0, 27.1, 22.8;IR ν: 2985IR ν: , 2953IR ν: , 1478IR ν: , 1411IR ν: , 1365IR ν: , 1346IR ν: , 1332 2,2,6-三甲基苯并吡喃(3g) [6] : 144 mg, 无色液体, 8,129.9,128.8,128.0,120.7,117.1,74.0,33.0,27.0,22.6,20.6;HRMS (ESI) 8,142.3,126.2,124.4,120.0,116.7,74.1,34.1,33.1,31.8,…”