Ultrasound-Assisted Expedient and Green Synthesis of a New Series of Diversely Functionalized 7-Aryl/heteroarylchromeno[4,3-d]pyrido[1,2-a]pyrimidin-6(7H)-ones via One-Pot Multicomponent Reaction under Sulfamic Acid Catalysis at Ambient Conditions

Abstract

An ultrasound-assisted, highly efficient, simple, and straightforward protocol for one-pot synthesis of a new series of pharmaceutically relevant and diversely functionalized 7-aryl/heteroarylchromeno­[4,3-d]­pyrido­[1,2-a]­pyrimidin-6­(7H)-ones (4) was developed based on a three-component tandem reaction between 4-hydroxycoumarin (1), substituted aromatic aldehydes (2), and 2-aminopyridines (3) in the presence of sulfamic acid as a low-cost and ecofriendly solid acid-catalyst in aqueous ethanol at ambient conditions. Expedient metal-free synthesis, good to excellent yields, energy efficiency, use of aqueous ethanol as reaction medium, easy isolation of products, no need of column chromatographic purification, high atom-economy and low E-factor, high turnover number, ecofriendliness, and operational simplicity are some of the salient features of this newly developed protocol.

Ultrasound-assisted transition-metal-free catalysis: a sustainable route towards the synthesis of bioactive heterocycles

“…Brahmachari et al 190 established a simple, straightforward, and environmentally benign multicomponent approach for the practical construction of structurally divergent chromeno[4,3- d ]pyrido[1,2- a ]pyrimidin-6(7 H )-ones ( Scheme 42 ). By introducing 20 mol% of sulphamic acid (NH 2 SO 3 H) as an organocatalyst, they executed an atom- and pot-economic reaction between readily accessible 4-hydroxycoumarin 146, substituted aldehydes 20, and 2-aminopyridine 147 with an equimolar mixture of aqueous ethanolic solution (1 : 1, v/v) under ultrasound irradiation under ambient conditions, which provided the respective products 148 in 70–97% yields.…”

Ultrasound irradiation in heterocycle synthesis: An overview

“…A green strategy to access differently substituted 7‐aryl/heteroarylchromeno[4,3‐ d ]pyrido[1,2‐ a ]pyrimidin‐6(7 H )‐ones was put forward by Brahmachari et al in 2018 [46]. The sulfamic acid‐catalyzed multicomponent reaction of 4‐hydroxycoumarin, aryl aldehydes, and 2‐aminopyridine in ethanol afforded the desired product in good to excellent yields under ultrasound irradiation within 8–32 min.…”

Application of 2-Aminopyridines in the Synthesis of Five- and Six-Membered Azaheterocycles

“…例如, 董德文课题 组 [91] 基于 2-氨基吡啶构建吡啶并[1,2-a]嘧啶的多组分反 应, 也是化学工作者们的研究热点 [92][93] , 其中一个底物 可以是酯类化合物 [94] . 例如, Brahmachari 课题组 [95] 发 现, 4-羟基香豆素与 2-氨基吡啶 1、 芳香醛 9 在超声辐射 的条件下, 通过一锅法策略进行反应, 能得到 4-芳基取 代吡啶并[1,2-a]嘧啶-4-酮(Eq. 15).…”