Here we report a transition metal– and oxidant–free annulation cascade method for the synthesis of chromeno–isoxazoles. The annulation reaction involves easily accessible starting materials, 3-nitro-2H-chromene and α-chloro aldehyde, yielding the structurally intriguing framework, chromeno[3,4-c]isoxazoles employed by tripotassium phosphate as a base. The isoxazole ring construction over the 2H–chromene unit is believed to occur via a series of multiple reaction sequences. Here, the enolate generation/Michael addition/C−Cl bond cleavage/oxy–anionic addition to reactive tethered-aldehyde/deformylation via retro–C−C and N−O bond cleavages are the most possible sequences which furnish the desired end–product in good chemical yields. The multiple reaction sequences occur in one-pot at mild conditions, supported by experimental results and a few control experiments including DFT studies. This process exhibits a broad substrates scope illustrating good functional group compatibility towards both the nitrochromenes and aldehydes, and thus prove to be a general and efficient protocol for the synthesis of chromeno[3,4–c]isoxazoles. Overall, the use of nitrochromene as the limiting reagent, noteworthy functional group tolerance, scalability including great applications like chiral pool strategy towards the synthesis of enantioenriched chromeno-isoxazole are the additional features.

在这里，我们报告了一种用于合成色并异恶唑的无过渡金属和氧化剂的环化级联方法。成环反应涉及容易获得的起始原料，3-硝基-2H-色烯和α-氯醛，产生结构有趣的框架，即以磷酸三钾为碱的色并[3,4- c ]异恶唑。 2 H-色烯单元上的异恶唑环结构被认为是通过一系列多重反应顺序发生的。在这里，烯醇化物生成/迈克尔加成/C-Cl键断裂/氧阴离子加成到反应性束缚醛/通过逆-C-C和N-O键断裂的去甲酰化是提供所需最终产物的最可能的序列具有良好的化学收率。多个反应序列在温和条件下在一锅中发生，并得到实验结果和包括 DFT 研究在内的一些对照实验的支持。该过程表现出广泛的底物范围，说明对硝基色烯和醛都具有良好的官能团相容性，因此被证明是合成色并[3,4- c ]异恶唑的通用且有效的方案。总体而言，使用硝基色烯作为限制试剂、值得注意的官能团耐受性、可扩展性（包括用于合成对映体富集的色异恶唑的手性池策略等重大应用）是其他特征。