Access to Furo[2,3‐ b ]pyridines by Transition‐Metal‐Free Intramolecular Cyclization of C3‐substituted Pyridine N ‐oxides

2018 ◽  
Vol 7 (5) ◽  
pp. 879-882 ◽  
Author(s):  
Dong Wang ◽  
Meng Shen ◽  
Yuxi Wang ◽  
Jianyong Hu ◽  
Junjie Zhao ◽  
...  
Keyword(s):  
Transition Metal ◽  
Intramolecular Cyclization ◽  
Metal Free

Synthesis of Imidazo[1,5-a]quinolines via Metal-Free Oxidative Amination of sp3 C–H Bonds

Synthesis ◽  
2018 ◽  
Vol 50 (14) ◽  
pp. 2761-2767 ◽  
Author(s):  
Chen Ma ◽  
Huanhuan Liu ◽  
Xinfeng Wang
Keyword(s):  
Amino Acids ◽  
Transition Metal ◽  
Intramolecular Cyclization ◽  
Efficient Synthesis ◽  
Oxidative Amination ◽  
Metal Free ◽  
Oxidation System

A novel oxidative amination of sp3 C–H bonds was developed for the efficient synthesis of imidazo[1,5-a]quinolines from readily available α-amino acids and (2-azaaryl)methanes. This domino protocol, which was established in a TBAI-TBHP oxidation system, includes transition-metal-free decarboxylation and intramolecular cyclization. This method represented a new avenue for the synthesis of N-heterocycles using 2-methylquinolines as the synthon of quinoline-2-carbaldehydes.

scholarly journals Base-Catalyzed Synthesis of Flavones via Thiol-Assisted Sequential Demethylation/Cyclization of 1-(2-methoxyphenyl)prop-2-yn-1-ones

2021 ◽  
Author(s):  
Ritiele Heck ◽  
Thiago Anjos ◽  
Maira R Giehl ◽  
Ricardo F Schumacher ◽  
Benhur Godoi
Keyword(s):  
Reaction Time ◽  
Secondary Metabolites ◽  
Transition Metal ◽  
Intramolecular Cyclization ◽  
Important Class ◽  
Short Reaction Time ◽  
Metal Free ◽  
Synthetic Strategy ◽  
Pharmacologically Active ◽  
Active Substances

Flavone and analogues represent an important class of biologically and pharmacologically active substances commonly found in the composition of diverse plants as part of the class of secondary metabolites. Herein, we have demonstrated an efficient and regioselective synthetic strategy for the preparation of functionalized flavones through sequential demethylation/6-endo-dig intramolecular cyclization of propyn-1-ones, using catalytic amounts of base in the presence of a thiol, by employing NMP as the solvent. The reactions proceeded smoothly under transition-metal-free and open to air conditions, furnishing the desired six-membered heterocycles in moderate to excellent yields, in short reaction time.

Transition-metal-free C–C σ-bond activation of α-aryl ketones and subsequent Zn-catalyzed intramolecular cyclization: synthesis of tetrasubstituted furans

2019 ◽  
Vol 17 (10) ◽  
pp. 2725-2733 ◽  
Author(s):  
Yang Yuan ◽  
Hailu Tan ◽  
Lingkai Kong ◽  
Zhong Zheng ◽  
Murong Xu ◽  
...  
Keyword(s):  
Transition Metal ◽  
Intramolecular Cyclization ◽  
Bond Activation ◽  
Metal Free ◽  
Aryl Ketones ◽  
Single Bonds

Atom-economical synthesis of tetrasubstituted furans from α-aryl ketones and alkynones through base-promoted cleavage of unstrained C–C single bonds of ketones and subsequent Zn-catalyzed cyclization.

Synthesis of benzo[b]chalcogenophenes fused to selenophenes via intramolecular electrophilic cyclization of 1,3-diynes

2021 ◽  
Author(s):  
Paola S. Hellwig ◽  
Jonatan S. Guedes ◽  
Angelita M. Barcellos ◽  
Raquel G. Jacob ◽  
Claudio C. Silveira ◽  
...  
Keyword(s):  
Transition Metal ◽  
Intramolecular Cyclization ◽  
Electrophilic Cyclization ◽  
Metal Free

We describe herein an alternative and transition-metal-free procedure for the access of benzo[b]chalcogenophenes fused to selenophenes via intramolecular cyclization of 1,3-diynes promoted by Oxone®.

scholarly journals Last Decade of Unconventional Methodologies for the Synthesis of Substituted Benzofurans

Molecules ◽  
2020 ◽  
Vol 25 (10) ◽  
pp. 2327 ◽  
Author(s):  
Lucia Chiummiento ◽  
Rosarita D’Orsi ◽  
Maria Funicello ◽  
Paolo Lupattelli
Keyword(s):  
Natural Products ◽  
Transition Metal ◽  
Intramolecular Cyclization ◽  
Bond Formation ◽  
Transition Metal Catalysis ◽  
Metal Catalysis ◽  
Metal Free ◽  
Bond Forming ◽  
Intermolecular Cyclization

This review describes the progress of the last decade on the synthesis of substituted benzofurans, which are useful scaffolds for the synthesis of numerous natural products and pharmaceuticals. In particular, new intramolecular and intermolecular C–C and/or C–O bond-forming processes, with transition-metal catalysis or metal-free are summarized. (1) Introduction. (2) Ring generation via intramolecular cyclization. (2.1) C7a–O bond formation: (route a). (2.2) O–C2 bond formation: (route b). (2.3) C2–C3 bond formation: (route c). (2.4) C3–C3a bond formation: (route d). (3) Ring generation via intermolecular cyclization. (3.1) C7a-O and C3–C3a bond formation (route a + d). (3.2) O–C2 and C2–C3 bond formation: (route b + c). (3.3) O–C2 and C3–C3a bond formation: (route b + d). (4) Benzannulation. (5) Conclusion.

Transition-Metal-Free Synthesis of Pyrrolo[1,2-a]pyrazines via Intramolecular Cyclization of N-Propargyl(pyrrolyl)enaminones

Synthesis ◽  
2017 ◽  
Vol 49 (17) ◽  
pp. 4065-4081 ◽  
Author(s):  
Lyubov Sobenina ◽  
Elena Sagitova ◽  
Igor Ushakov ◽  
Boris Trofimov
Keyword(s):  
Transition Metal ◽  
Intramolecular Cyclization ◽  
Room Temperature ◽  
Cross Coupling ◽  
Metal Free ◽  
Key Steps

A concise transition-metal-free strategy for the synthesis of pyrrolo[1,2-a]pyrazines with enone substituents has been developed. It includes the following key steps: (a) cross-coupling of pyrroles with acyl(bromo)acetylenes in solid alumina at room temperature to give 2-(acylethynyl)pyrroles; (b) addition of propargylamine to the above acetylenes to form the corresponding N-propargylenaminones; and (c) chemo- and stereoselective base-catalyzed (Cs2CO3/DMSO) intramolecular cyclization of the synthesized propargylic derivatives to form (acylmeth­ylidene)pyrrolo[1,2-a]pyrazines of Z-configuration.

scholarly journals Transition-metal-free base catalyzed intramolecular cyclization of 2-ynylphenols for efficient and facile synthesis of 2-substituted benzo[b]furans

RSC Advances ◽  
2018 ◽  
Vol 8 (50) ◽  
pp. 28637-28641 ◽  
Author(s):  
Yong Liu ◽  
Tao Lu ◽  
Wei-Fang Tang ◽  
Jian Gao
Keyword(s):  
Transition Metal ◽  
Intramolecular Cyclization ◽  
Free Base ◽  
Facile Synthesis ◽  
Metal Free

An efficient and practical transition-metal-free synthesis of 2-substituted benzo[b]furans catalyzed by readily accessible base was developed with broad substrates scope.

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