Substrate‐Controlled [5+1] Annulation of 5‐Amino‐1H‐phenylpyrazoles with Alkenes: Divergent Synthesis of Multisubstituted 4, 5‐Dihydropyrazolo[1, 5‐a]quinazolines. Issue 26 (5th June 2020)

• Record Type: Journal Article
• Authors: Jiang, Xunyuan; Wei, Xiaoyi; Lin, Fei; Zhang, Zhixiang; Yao, Guangkai; Yang, Shuai; Zhao, Weijing; Zhao, Chen; Xu, Hanhong
• Is Part Of: European journal of organic chemistry. Issue 26(2020)
• Page Start: 3997
• Page End: 4003
• Publication Date: 2020-06-05
• Subjects: Annulation -- 4, 5‐Dihydropyrazolo[1, 5‐a]quinazolines -- Nucleophilic aromatic substitution -- Truce‐Smiles rearrangement -- Alkenes; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.202000536
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract : A new and efficient [5+1] annulation reaction for the first synthesis of 5, 5‐disubstituted 4, 5‐dihydropyrazolo[1, 5‐ a ]quinazolines is described. This transition‐metal‐free tandem cyclization was performed with 5‐amino‐1 H ‐phenylpyrazole and readily available electron‐deficient olefinic ester. The reaction proceeds via an aza‐Michael addition/Truce‐Smiles rearrangement/SN Ar cyclization pathway, which was verified by DFT calculations. The participation of Truce‐Smiles rearrangement is substrate dependent and could prompt the process of cascade reactions. It is also the first report of alkenes acting as one‐carbon synthons for [5+1] hetero‐annulations. Abstract : With C=C double bonds as one‐carbon synthons, an efficient [5+1] hetero‐annulation of 5‐amino‐1 H ‐phenylpyrazoles with electron‐deficient olefinic esters was developed, allowing the first and divergent synthesis of 5, 5‐disubstituted 4, 5‐dihydropyrazolo[1, 5‐ a ]quinazolines.