Article
Chemistry, Organic
Bai Shi, Fangyi Jin, Qi Lv, Xinrong Zhou, Zhixiao Liao, Chenxia Yu, Kai Zhang, Changsheng Yao
Summary: A N-heterocyclic carbene (NHC) catalyzed formal [3 + 3] annulation reaction between & delta;-acetoxy allenoates and 1C,3O-bisnucleophiles has been developed for the synthesis of highly functionalized 4H-(fused)pyrans, with a broad substrate scope (30 examples, up to 77% yield).
ORGANIC & BIOMOLECULAR CHEMISTRY
(2023)
Article
Chemistry, Organic
Chunjie Ni, Shiyu Pan, Chen Yuan, Shuya Qin
Summary: Amine-catalyzed [3 + 3] annulations of β-acetoxyallenoates with 1C,3N-bisnucleophiles have been successfully established, providing a convenient and efficient method to synthesize novel 1,2-fused benzimidazole derivatives in moderate to good yields. Preliminary attempts on the asymmetric version of this reaction using cinchona alkaloid-based tertiary amines have also been explored.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Organic
Sachin Chauhan, Shubham Debnath, K. C. Kumara Swamy
Summary: This study reports the Lewis base dependent (3 + 3) annulation of delta-acetoxy allenoates with benzofuranone, pyrazolone, and Boc-protected oxindole. In the presence of catalytic DBU, oxindole, benzofuranone, and pyrazolone undergo (3 + 3) annulation with delta-acetoxy allenoates via 6-exo-dig cyclization at room temperature (25 degrees C) to afford fused pyran scaffolds. On the other hand, by employing catalytic DMAP, the reaction between N-Boc-oxindole and delta-acetoxy allenoates goes through 6-endo-dig cyclization, leading to distinct dihydropyrans that contain an exocyclic double bond; similar products were also obtained by using benzofuranone and pyrazolone.
ORGANIC & BIOMOLECULAR CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Yannan Zhu, Zhili Xu, Yi-Ning Wang
Summary: The phosphine-catalyzed [5+1] annulation reaction of beta'-acetoxy allenoates with 1,5-dinucleophiles has been achieved for the first time. This reaction provides a novel and efficient method to synthesize functionalized tetrahydroquinolines in good to high yields under mild reaction conditions in the presence of PPh3 and K3PO4.
CHEMICAL COMMUNICATIONS
(2023)
Article
Chemistry, Applied
Shubham Debnath, A. Sanjeeva Kumar, Sachin Chauhan, K. C. Kumara Swamy
Summary: Lewis base dependent (3+3) annulations of beta & PRIME;/delta-acetoxy allenoates with iminoindolines can yield alpha-carbolines with varying substituents depending on the base used and reaction conditions. The reaction involves key steps of cyclization, elimination, and trapping. Plausible reaction mechanism has been supported by control experiments and HRMS studies.
ADVANCED SYNTHESIS & CATALYSIS
(2022)
Article
Chemistry, Organic
Shabbir Ahmed Khan, A. Sanjeeva Kumar, K. C. Kumara Swamy
Summary: DBU-catalyzed spiro-annulation and ring expansion/dominoreaction of delta-acetoxy allenoates with cycl-2-ene-N-sulfonyl hydrazides led to ring-expanded products. On the other hand, cycl-3-ene/ane-N-sulfonyl hydrazones under similar conditions gave pyrazolecores. The key intermediates of spirocyclic and dienyl-amine were isolated and characterized. An extension to (R)-(-)-carvone-derived sulfonyl hydrazide also resulted in ring expansion and formation of pyrazoloazepine.
Article
Chemistry, Multidisciplinary
Mingyue Wu, Zhaobin Han, Huanzhen Ni, Nengzhong Wang, Kuiling Ding, Yixin Lu
Summary: Highly enantioselective and chemodivergent domino reactions have been developed between gamma-substituted allenoates and activated alkenes. Different types of chiral products, with biological relevance and synthetic importance, can be obtained by controlling the structural differences of the substrates under virtually identical reaction conditions.
Article
Chemistry, Organic
Dongqiu Li, Xiaoqian Zhang, Wendan Han, Jiao Jiao, Yuhai Tang, Silong Xu
Summary: This study presents a Lewis base-catalyzed annulation reaction using hepta-2,3,5-trienedioates as substrates. Mild conditions allow for the construction of exocyclic olefinic cyclopentenes through a [3+2] annulation with electron-deficient alkenes, obtaining good yields and moderate E:Z ratios. This reaction involves a tandem [3+2] cyclization and double bond migration, with the ε-ester playing a crucial role in both processes. Additionally, it demonstrates a substrate-controlled divergent reactivity compared to a previous report.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Organic
Xue Song, Yangxu Chen, Fangfang Lu, Kai Zhang, Chenxia Yu, Tuanjie Li, Changsheng Yao
Summary: A facile NHC-catalyzed [2 + 4] annulation of allenoates with 2,3-dioxypyrrolidine derivatives has been discovered, providing a new approach for the synthesis of highly substituted pyranopyrrole compounds with moderate to good yields, high atom economy, and mild reaction conditions.
ORGANIC & BIOMOLECULAR CHEMISTRY
(2022)
Article
Chemistry, Organic
Shabbir Ahmed Khan, A. Sanjeeva Kumar, K. C. Kumara Swamy
Summary: Under the catalysis of DABCO, pyridine, or tetra-n-butyl ammonium bromide (TBAB), the same 5-acetoxy allenoates and thioamides undergo different annulations to give dihydrothiophene, thiopyran, or thiazole motifs. Pyridine-catalyzed [3 + 2] annulation leads to essentially single diastereomers of dihydrothiophenes. In contrast, allenoates deliver thiopyran motifs in good to high yields through 6-exo-dig cyclization under DABCO catalysis. In the thiazole forming [3 + 2] annulation, tetra-n-butyl ammonium bromide (TBAB) facilitates addition-elimination and 5-exo-trig cyclization, resulting in thiazole cores exclusively with a Z-isomeric exocyclic double bond.
JOURNAL OF ORGANIC CHEMISTRY
(2022)
Article
Chemistry, Organic
Yunpeng Chu, Meng Wu, Fang Hu, Panpan Zhou, Zhengqiang Cao, Xin-Ping Hui
Summary: The first atroposelective synthesis of pyrrolo[3,4-b]pyridines catalyzed by N-heterocyclic carbene has been achieved, leading to a wide range of chiral atropisomers with high yields and excellent enantioselectivities (96-99% enantiomeric excess). Experimental results and density functional theory calculations demonstrate the high thermal stability of the C-N axial chirality in the product.
Article
Chemistry, Organic
Shubham Debnath, A. Sanjeeva Kumar, Sachin Chauhan, K. C. Kumara Swamy
Summary: The reactivity of 2-sulfonamidoindoles with acetoxy allenoates under phosphine catalysis is dependent on the position of the acetoxy (OAc) group on the allenoate. The reaction can lead to different annulation products depending on the temperature-controlled conditions.
JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Chemistry, Multidisciplinary
Xin He, Pengchen Ma, Yuhai Tang, Jing Li, Shenyu Shen, Martin J. Lear, K. N. Houk, Silong Xu
Summary: We report a phosphine-catalyzed (3 + 2) annulation of cyclopropenones with various electrophilic pi systems, yielding products including butenolides, butyrolactams, maleimides, and iminomaleimides in high yields with a wide range of substrates. An alpha-ketenyl phosphorous ylide is identified as the key intermediate, which undergoes preferential catalytic cyclization with aldehydes. This phosphine-catalyzed activation of cyclopropenones provides a versatile C-3 synthon for formal cycloadditon reactions.
Article
Chemistry, Organic
Ningtao He, Jilong Zhang, Xiaohe Miao, Dehai Li, De Wang
Summary: In this study, the first organophosphine-catalyzed allylic alkylation of (hetero)arylalkynes with various carbo-nucleophiles is described. The method is highly atom economical and compatible with a wide range of substrates, leading to the concise total synthesis of natural product (& PLUSMN;)-esermethole.
Article
Chemistry, Organic
Zhan-Cai Ma, Lin-Wen Wei, Yuan Huang
Summary: We have developed a highly efficient stereodivergent [4 + 2] annulation reaction using palladium catalysis to synthesize N-heterocycles with 1,3-nonadjacent stereogenic centers. The diastereoselectivity of the reaction is dependent on the polarity of solvents used. Additionally, good enantioselectivities were achieved by employing the chiral ligand Wingphos.
