Catalyst-free synthesis of diversely substituted 6H-benzo[c]chromenes and 6H-benzo[c]chromen-6-ones in aqueous media under MWI

Abstract

In this paper, a catalyst-free synthesis of diversely substituted 6H-benzo[c]chromenes and 6H-benzo[c]chromen-8-ols via cascade reactions of 2-(2-(allyloxy)phenyl)furan and 2-(2-( prop-2-ynyloxy)phenyl)furan, featured with intramolecular Diels-Alder reactions of furan with unactivated alkene/alkyne in aqueous media under MWI, was developed. In addition, an environmentally friendly oxidation of 6Hbenzo[c]chromenes into the corresponding benzo[c]chromen-6-ones using aqueous H 2 O 2 as an oxidant, in the absence of any activator/catalyst, was also revealed. † Electronic supplementary information (ESI) available. See

Diels–Alder Cycloaddition Reactions in Sustainable Media

“…A series of diversely substituted 6H-benzo[c]chromenes 134 have been prepared via intramolecular Diels-Alder reactions of furan with unactivated alkenes in an aqueous medium under MW irradiation (Scheme 30) [104]. The reaction pathway involves the initial formation of cycloadduct 132 which undergoes ring-opening to give intermediate 133, followed by aromatization to yield the desired 6H-benzo[c]chromenes 134 in yields ranging from 45 to 85%.…”

Visible-Light Mediated Synthesis of 6H-Benzo[c]chromenes

“…传统上合成 这类化合物主要通过 Suzuki-Miyaura, Negishi, Kumada-Corriu 以及 Hiyama 偶联反应得以实现 [4] (Path 1), 然 而这些方法底物不易制备且具有较大局限性, 不利于 6H-苯并 [c]苯并吡喃类衍生物的简单、绿色合成. 近几 年来, 化学家们利用过渡金属催化 C-H 芳基化反应 [5] (Path 2)、分子内 S N Ar 反应 [6] (Path 3)以及 Diels-Alder 反 应 [7] (Path 4)分别实现了各种各样 6H-苯并 [c]苯并吡喃类 化合物的有效合成(Scheme 1). 这些方法在很大程度上 拓宽了 6H-苯并 [c]苯并吡喃类衍生物的合成途径,也存 在许多缺陷, 如需要添加化学计量的碱, 反应要在高温 下进行等.…”

“…5,154.5,137.6,134.5,134.2,132.2,131.4,129.3,129.2,128.9,128.7,127.9,127.3,127.1,125.3,124.5,123.1,123.0,122.7,122.1,121.9,121.5,117.4,117.3,69.8,68.5,23.1,21.3. HRMS (ESI) (d, J＝2.6 Hz, 1 H), 5.11 (s, 2H), 5.03 (s, 0.26H), 3.96 (s, 0.39H), 3.86 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ: 159.4, 156.5, 155.2, 153.9, 134.5, 133.0, 129.5, 128.7, 128.6, 128.4, 123.5, 123.0, 122.9, 122.6, 122.2, 121.7, 118.8, 117.3, 117.2, 116.8, 114.8, 113.9, 111.4, 111.0, 68.9, 68.5, 55.6, 55.4 (d,J＝247 Hz,1C),155.9 (d,J＝12.1 Hz,1C),130.5,129.5,128.6,127.6,124.7,124.4 (d,J＝10.0 Hz,1C),121.7,119.3 (d,J＝3.1 Hz,1C),109.3 (d,J＝22. [7] (2i): 无色液体, 收率 83%. 1 H NMR (400 MHz, CDCl 3 ) δ: 7.59 (d,J＝2.6 Hz,1H),…”

“…2-甲基-6H-苯并[c]苯并吡喃 [7] (2j): 无色液体, 收率 77%. 1 H NMR (400 MHz, CDCl 3 ) δ: 7.73 (d, J＝7.7 Hz, 1H), 7.58 (d, J＝1.6 Hz, 1H), 7.41 (t, J＝8.2 Hz, 1H), 7.31 (td, J＝7.5, 1.1 Hz, 1H), 7.18 (dd, J＝7.5, 0.6 Hz, 1H), 7.08 (dd, J＝8.2, 1.5 Hz, 1H), 6.94 (d,J＝8.2 Hz,1H),…”

Direct multicomponent synthesis of benzocoumarins

“…Other efficient alternative approaches reported in literature involve tandem cycloaddition reactions to form C ring of benzo[c]courmarin 1 (Fig. 2, path c) (Pottie et al, 2011;He et al, 2012). In this latter case, the Diels-Alder reaction is especially useful, as it offers the greatest potential for diversity (Pottie et al, 2011).…”