One-pot regioselective annulation toward 3,4-dihydro-3-oxo-2H-1,4-benzoxazine scaffolds under controlled microwave heating
摘要:
An efficient and general synthesis of 2-alkyl-3,4-dihydro-3-oxo-2H-1,4-benzoxazines under controlled microwave heating has been established. It consists of a microwave-assisted reductive N-arylmethylation of substituted 2-aminophenols with aromatic aldehydes followed by a one-pot base-mediated regioselective O-alkylation of the N-arylmethyl-2-aminophenois with 2-bromoalkanoates to give the acyclic intermediates, which cyclize spontaneously to furnish the benzoxazine scaffolds in good to excellent yields. It was found that microwave heating over 180 degrees C was necessary for ring closure of the acyclic intermediates possessing an electron-withdrawing group. (c) 2006 Elsevier Ltd. All rights reserved.
One-pot regioselective annulation toward 3,4-dihydro-3-oxo-2H-1,4-benzoxazine scaffolds under controlled microwave heating
作者:Gaofeng Feng、Jinlong Wu、Wei-Min Dai
DOI:10.1016/j.tet.2005.12.059
日期:2006.5
An efficient and general synthesis of 2-alkyl-3,4-dihydro-3-oxo-2H-1,4-benzoxazines under controlled microwave heating has been established. It consists of a microwave-assisted reductive N-arylmethylation of substituted 2-aminophenols with aromatic aldehydes followed by a one-pot base-mediated regioselective O-alkylation of the N-arylmethyl-2-aminophenois with 2-bromoalkanoates to give the acyclic intermediates, which cyclize spontaneously to furnish the benzoxazine scaffolds in good to excellent yields. It was found that microwave heating over 180 degrees C was necessary for ring closure of the acyclic intermediates possessing an electron-withdrawing group. (c) 2006 Elsevier Ltd. All rights reserved.
K<sub>2</sub>CO<sub>3</sub>/H<sub>2</sub>O in [omim][BF<sub>4</sub>] Ionic Liquid: A Green Medium for Efficient Room-Temperature Synthesis of<i>N</i>-Substituted 1,4-Benzoxazin-3-ones
A medium consisting of K2CO3 and H2O in [omim][BF4] ionicliquid (IL) was used to synthesize N‐substituted 2H‐benzo[b][1,4]oxazin‐3(4H)‐one derivatives from their corresponding o‐aminophenols and 2‐bromoalkanoates. As a result, chemoselective formation of benzoxazinones in high yields has been observed at roomtemperature. After the reactions and separation of the products, the IL was recovered and
使用在[omim] [BF 4 ]离子液体(IL)中由K 2 CO 3和H 2 O组成的介质合成N-取代的2 H-苯并[ b ] [1,4]恶嗪-3(4 H)-一种来自其相应的邻-氨基苯酚和2-溴代链烷酸酯的衍生物。结果,在室温下已观察到高产率的苯并恶嗪酮的化学选择性形成。在反应和产物分离之后,回收了IL,并成功地将其重新用于随后的反应中,而没有明显的活性损失。