Efficient Syntheses of (Thio)phosphonylated Isobenzofurans by Tandem Nucleophilic Addition and Regioselective 5‐exo‐dig Addition to Carbon‐Carbon Triple Bond: Cooperative Effect to 1,8‐Diazabicyclo[5.4.0]undec‐7‐ene (DBU) |
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| Authors: | Fei Wang Yadan Wang Lingchao Cai Zhiwei Miao Ruyu Chen |
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| Affiliation: | 1. State Key Laboratory and Institute of Elemento‐Organic Chemistry, Nankai University, Tianjin 300071, People's Republic of China, Fax: (+86)‐22‐2350‐2351;2. Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Tsinghua University, Beijing 100084, People's Republic of China |
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| Abstract: | The tandem nucleophilic addition‐cyclization reaction of o‐alkynylbenzaldehydes or o‐alkynylacetophenones 2 with dialkyl phosphites or dialkyl phosphonothioates 1 took place very smoothly in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) in THF at room temperature. In all cases, the reaction proceeded in a regioselective manner leading to the 5‐exo‐dig products 3 in excellent yields. The phenomenon of a 1,5‐sigmatropic hydrogen shift or a 1,5‐sigmatropic methyl shift was observed in this reaction depending on the different substituent groups such as R3 in the o‐alkynylbenzaldehyde or o‐alkynylacetophenone 2 substrates. |
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| Keywords: | cyclization reaction 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) regioselective 5‐exo‐dig addition tandem nucleophilic addition |
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