scholarly journals A cascade double 1,4-addition/intramolecular annulation strategy for expeditious assembly of unsymmetrical dibenzofurans

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Xinwei He ◽  
Ruxue Li ◽  
Pui Ying Choy ◽  
Mengqing Xie ◽  
Jiahui Duan ◽  
...  
Keyword(s):  
Transition Metal ◽  
Late Stage ◽  
Functional Group ◽  
Conjugate Addition ◽  
Carbon Structure ◽  
Metal Free ◽  
Air Atmosphere ◽  
Efficient Access ◽  
Synthetic Routes ◽  
Metal Catalyzed

AbstractExisting synthetic routes for accessing dibenzofuran core have intrinsic regioselectivity, limiting the substitution patterns available in heteropolycyclic arene products. Here we report a double 1,4-conjugate addition/intramolecular annulation cascade reaction between propargylamines and two equivalents of imidazolium methylides that allows efficient access of structurally versatile dibenzofurans. This transition metal-free protocol proceeds smoothly under bench-top air atmosphere and offers easy manipulation of substituents on the dibenzofuran core, and also provides good-to-excellent product yields with good functional group tolerance, particularly the –Br and –Cl groups which are often incompatible with existing metal-catalyzed C–C and/or C–O bond ring-forming processes. It is worth noting that ladder-type π-systems with all-arene quarternary carbon structure can be straightforwardly generated upon simple late-stage functionalization.

scholarly journals Recent Advances in Transition-Metal-Free (4+3)-Annulations

Synthesis ◽  
2021 ◽  
Author(s):  
Heather Lam ◽  
Mark Lautens ◽  
Xavier Abel-Snape ◽  
Martin F. Köllen
Keyword(s):  
Transition Metal ◽  
Boronic Acid ◽  
Lewis Acids ◽  
Acid Catalysis ◽  
Heterocyclic Carbenes ◽  
Bronsted Acids ◽  
Metal Free ◽  
Previous Review ◽  
Dual Activation ◽  
Metal Catalyzed

Abstract(4+3)-Annulations are incredibly versatile reactions which combine a 4-atom synthon and a 3-atom synthon to form both 7-membered carbocycles as well as heterocycles. We have previously reviewed transition-metal-catalyzed (4+3)-annulations. In this review, we will cover examples involving bases, NHCs, phosphines, Lewis and Brønsted acids as well as some rare examples of boronic acid catalysis and photocatalysis. In analogy to our previous review, we exclude annulations involving cyclic dienes like furan, pyrrole, cyclohexadiene or cyclopentadiene, as Chiu, Harmata, Fernándes and others have recently published reviews encompassing such substrates. We will however discuss the recent additions (2010–2020) to the literature on (4+3)-annulations involving other types of 4-atom-synthons.1 Introduction2 Bases3 Annulations Using N-Heterocyclic Carbenes3.1 N-Heterocyclic Carbenes (NHCs)3.2 N-Heterocyclic Carbenes and Base Dual-Activation4 Phosphines5 Acids5.1 Lewis Acids5.2 Brønsted Acids6 Boronic Acid Catalysis and Photocatalysis7 Conclusion

Direct and metal-free oxidative amination of sp3 C–H bonds for the construction of 2-hetarylquinazolin-4(3H)-ones

2016 ◽  
Vol 3 (9) ◽  
pp. 1096-1099 ◽  
Author(s):  
Huanhuan Liu ◽  
Tianran Zhai ◽  
Shiteng Ding ◽  
Yalei Hou ◽  
Xiangyu Zhang ◽  
...  
Keyword(s):  
Transition Metal ◽  
Functional Group ◽  
New Method ◽  
Oxidative Amination ◽  
Metal Free ◽  
Mild Conditions

New method for synthesis of 2-hetarylquinazolin-4(3H)-ones from 2-aminobenzamides and (2-azaaryl)methanes under transition-metal free conditions, featuring a wide substrate scope with a broad range of functional group tolerance under mild conditions.

Diiiodine/Potassium Persulfate Mediated Synthesis of 1,2,3-Thiadiazoles from N-Tosylhydrazones and a Thiocyanate Salt as a Sulfur Source under Transition-Metal-Free Conditions

Synlett ◽  
2021 ◽  
Author(s):  
Yadong Sun ◽  
Ablimit Abdukader ◽  
Yuhan Lu ◽  
Chenjiang Liu
Keyword(s):  
Transition Metal ◽  
Efficient Method ◽  
Room Temperature ◽  
Functional Group ◽  
Ammonium Thiocyanate ◽  
Potassium Persulfate ◽  
Sulfur Source ◽  
Coupling Reactions ◽  
Wide Scope ◽  
Metal Free

AbstractA highly efficient method for the synthesis of 1,2,3-thiadiazoles has been developed by utilizing readily available tosylhydrazones and ammonium thiocyanate with ecofriendly EtOH as the solvent at room temperature. The reaction shows a wide scope of substrates and good functional-group tolerance. This protocol can be scaled up to a gram level and can be applied to coupling reactions with 4-(4-bromophenyl)-1,2,3-thiadiazole as the substrate.

Facile Access to Triazole-Fused 3,1-Benzoxazines Enabled by Metal-Free Base-Promoted Intramolecular C–O Coupling

Synthesis ◽  
2021 ◽  
Author(s):  
Yury N. Kotovshchikov ◽  
Stepan S. Tatevosyan ◽  
Gennadij V. Latyshev ◽  
Nikolay V. Lukashev ◽  
Irina P. Beletskaya
Keyword(s):  
Transition Metal ◽  
Functional Group ◽  
Cost Effective ◽  
Reductive Cleavage ◽  
Effective Procedure ◽  
Free Base ◽  
Metal Free ◽  
Fused Heterocycles ◽  
Convenient Approach

AbstractA convenient approach to assemble 1,2,3-triazole-fused 4H-3,1-benzoxazines has been developed. Diverse alcohol-tethered 5-iodotriazoles, readily accessible by a modified protocol of Cu-catalyzed (3+2)-cycloaddition, were utilized as precursors of the target fused heterocycles. The intramolecular C–O coupling proceeded efficiently under base-mediated transition-metal-free conditions, furnishing cyclization products in yields up to 96%. Suppression of the competing reductive cleavage of the C–I bond was achieved by the use of Na2CO3 in acetonitrile at 100 °C. This practical and cost-effective procedure features a broad substrate scope and valuable functional group tolerance.

Five-Membered Hetarene N-Oxides: Recent Advances in Synthesis and Reactivity

Synthesis ◽  
2021 ◽  
Author(s):  
Leonid Fershtat ◽  
Fedor Teslenko
Keyword(s):  
Transition Metal ◽  
Medicinal Chemistry ◽  
Materials Science ◽  
State Of The Art ◽  
Short Review ◽  
Advanced Materials ◽  
Metal Free ◽  
Recent Advances ◽  
Application Potential ◽  
Metal Catalyzed

Five-membered heterocyclic N-oxides attracted special attention due to their strong application potential in medicinal chemistry and advanced materials science. In this regard, novel methods for their synthesis and functionalization are constantly required. In this short review, recent state-of-the-art achievements in the chemistry of isoxazoline N-oxides, 1,2,3-triazole 1-oxides and 1,2,5-oxadiazole 2-oxides are briefly summarized. Main routes to transition-metal-catalyzed and metal-free functionalization protocols along with mechanistic considerations are outlined. Transformation patterns of the hetarene N-oxide rings as precursors to other nitrogen heterocyclic systems are also presented.

scholarly journals SO2F2-Mediated one-pot cascade process for transformation of aldehydes (RCHO) to cyanamides (RNHCN)

RSC Advances ◽  
2020 ◽  
Vol 10 (29) ◽  
pp. 17288-17292 ◽  
Author(s):  
Yiyong Zhao ◽  
Junjie Wei ◽  
Shuting Ge ◽  
Guofu Zhang ◽  
Chengrong Ding
Keyword(s):  
Transition Metal ◽  
Nitrogen Source ◽  
Functional Group ◽  
Cascade Process ◽  
One Pot ◽  
Metal Free ◽  
Work Up

Our gram-scale process uses abundant and inexpensive aldehydes, a clean nitrogen source, requires no additional carbon atoms, is transition-metal free, and features easy work-up and excellent functional group compatibility.

Direct Propargylation of ortho-Quinone Methides with Alkynyl Zinc Reagents: An Application to the One-Pot Synthesis of 2,3-Disubstituted Benzofurans

Synlett ◽  
2020 ◽  
Vol 31 (08) ◽  
pp. 818-822
Author(s):  
Hongjun Ren ◽  
Manman Sun ◽  
Jinyu Song ◽  
Lei Wang ◽  
Wenguang Yin ◽  
...  
Keyword(s):  
Transition Metal ◽  
Functional Group ◽  
Quinone Methides ◽  
One Pot ◽  
Metal Free ◽  
Efficient Strategy ◽  
One Pot Synthesis ◽  
Subsequent Cyclization ◽  
The One

A transition-metal-free propargylation of ortho-quinone methides (o-QMs) with alkynyl zinc reagents was achieved. A conjugate alkynylation of an o-QM and subsequent cyclization sequence in the presence of KOt-Bu for the synthesis of 2,3-disubstituted benzofurans in one pot was developed. This efficient strategy exhibits good functional-group compatibility and gives moderate to good yields. The present reaction might serve as an attractive method for the synthesis of polysubstituted benzofurans.

Transition-Metal-Free, Intermolecular Azidoheteroarylation of Alkenes: Efficient Access to β-Azidoalkylated Quinoxalinones and Preliminary Antifungal Evaluation Against Magnaporthe grisea

Synthesis ◽  
2020 ◽  
Vol 52 (16) ◽  
pp. 2395-2409
Author(s):  
Weiwei Qin ◽  
Zhaodong Li ◽  
Yiming Du ◽  
Yue Chen ◽  
Yun-Lin Liu
Keyword(s):  
Transition Metal ◽  
Magnaporthe Grisea ◽  
Single Step ◽  
Domino Reaction ◽  
Efficient Synthesis ◽  
Metal Free ◽  
Efficient Access ◽  
First Time ◽  
Antibacterial Evaluation ◽  
Addition Pathway

An efficient, PhI(OAc)2-mediated, radical azidoheteroarylation of alkenes under transition-metal-free conditions is reported by employing TMSN3 and quinoxalin-2(1H)-ones as coupling partners. This domino reaction allows an efficient synthesis of valuable orangoazides containing quinoxalin-2(1H)-one derivatives and could be extended to phosphinyl-alkylated quinoxalin-2(1H)-one in a single step in moderate to excellent yields under mild conditions, as demonstrated by the preliminary antibacterial evaluation against Magnaporthe grisea for the first time. Mechanistic studies revealed that this transformation undergoes a cascade addition pathway controlled by a polar radical.

scholarly journals Weinreb Amides as Directing Groups for Transition Metal-Catalyzed C-H Functionalizations

Molecules ◽  
2019 ◽  
Vol 24 (5) ◽  
pp. 830 ◽  
Author(s):  
Jagadeesh Kalepu ◽  
Lukasz Pilarski
Keyword(s):  
Transition Metal ◽  
Functional Group ◽  
Metal Catalysts ◽  
Mechanistic Studies ◽  
Weinreb Amides ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed

Weinreb amides are a privileged, multi-functional group with well-established utility in classical synthesis. Recently, several studies have demonstrated the use of Weinreb amides as interesting substrates in transition metal-catalyzed C-H functionalization reactions. Herein, we review this part of the literature, including the metal catalysts, transformations explored so far and specific insights from mechanistic studies.

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