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

scholarly journals Azaindole synthesis through dual activation catalysis with N-heterocyclic carbenes

2016 ◽  
Vol 52 (59) ◽  
pp. 9283-9286 ◽  
Author(s):  
Hayden A. Sharma ◽  
M. Todd Hovey ◽  
Karl A. Scheidt
Keyword(s):  
Transition Metal ◽  
Heterocyclic Carbenes ◽  
Metal Free ◽  
Dual Activation ◽  
High Yields

A convergent, transition-metal-free synthesis of 2-aryl-azaindoles enabled by carbene catalysis is reported with high yields and a wide substrate scope featuring previously inaccessible azaindoles.

Boronic acid catalysis

2019 ◽  
Vol 48 (13) ◽  
pp. 3475-3496 ◽  
Author(s):  
Dennis G. Hall
Keyword(s):  
Transition Metal ◽  
Boronic Acid ◽  
Acid Catalysis ◽  
Boronic Acids ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed

Although boronic acids are recognized primarily for their utility as reagents in transition metal-catalyzed transformations, other applications are emerging, including their use as reaction catalysts.

Merging gold catalysis, organocatalytic oxidation, and Lewis acid catalysis for chemodivergent synthesis of functionalized oxazoles from N-propargylamides

2017 ◽  
Vol 53 (75) ◽  
pp. 10366-10369 ◽  
Author(s):  
Shaoyu Mai ◽  
Changqing Rao ◽  
Ming Chen ◽  
Jihu Su ◽  
Jiangfeng Du ◽  
...  
Keyword(s):  
Transition Metal ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Acid Catalysis ◽  
Gold Catalysis ◽  
One Pot ◽  
Catalytic Systems ◽  
One Pot Synthesis ◽  
The One ◽  
Cationic Gold

Novel catalytic systems consisting of cationic gold complexes, N-hydroxyphthalimide (NHPI), and transition-metal-based Lewis acids have been developed for the one-pot synthesis of functionalized oxazoles.

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 Recent Synthesis Developments of Organoboron Compounds via Metal-Free Catalytic Borylation of Alkynes and Alkenes

Molecules ◽  
2018 ◽  
Vol 24 (1) ◽  
pp. 101 ◽  
Author(s):  
Yanmei Wen ◽  
Chunmei Deng ◽  
Jianying Xie ◽  
Xinhuang Kang
Keyword(s):  
Lewis Acids ◽  
Heterocyclic Carbenes ◽  
Lewis Base ◽  
Organoboron Compounds ◽  
Lewis Bases ◽  
Metal Free ◽  
Recent Synthesis

Diboron reagents have been traditionally regarded as “Lewis acids”, which can react with simple Lewis base to create a significant nucleophilic character in one of boryl moieties. In particular, bis(pinacolato)diboron (B2pin2) reacts with simple Lewis bases, such as N-heterocyclic carbenes (NHCs), phosphines and alkoxides. This review focuses on the application of trivalent nucleophilic boryl synthon in the selective preparation of organoboron compounds, mainly through metal-free catalytic diboration and the β-boration reactions of alkynes and alkenes.

scholarly journals Recent Developments in the Synthesis of Pyrido[1,2-a]benzimidazoles

Synthesis ◽  
2018 ◽  
Vol 50 (11) ◽  
pp. 2131-2149 ◽  
Author(s):  
Kamal Kapoor ◽  
Parthasarathi Das ◽  
Rajni Khajuria ◽  
Sk. Rasheed ◽  
Chhavi Khajuria
Keyword(s):  
Transition Metal ◽  
Medicinal Chemistry ◽  
Type I ◽  
Type Ii ◽  
Aromatic Rings ◽  
Metal Free ◽  
Wide Range ◽  
Recent Developments ◽  
Metal Catalyzed ◽  
Synthetic Approaches

Pyrido[1,2-a]benzimidazole is one of the most important azaheterocyclic compounds consisting of three fused aromatic rings. Molecules containing this core have displayed a wide range of applications in the field of medicinal chemistry. The synthesis of pyrido[1,2-a]benzimidazole and its derivatives has attracted organic chemists because of its tremendous utility in interdisciplinary branches of chemistry. In this context, this review discusses the main advances in the synthesis of pyrido[1,2-a]benzimidazoles via metal-mediated and metal-free reactions from 2000 to 2016.1 Introduction2 Synthetic Approaches to Pyrido[1,2-a]benzimidazoles2.1 Type I: Transition-Metal-Catalyzed Methods2.2 Type II: Metal-Free Approaches3 Conclusion

Recent Advances in Transition-Metal-Catalyzed (4+3)-Cycloadditions

Synthesis ◽  
2020 ◽  
Vol 52 (17) ◽  
pp. 2427-2449 ◽  
Author(s):  
Mark Lautens ◽  
Heather Lam
Keyword(s):  
Natural Products ◽  
Transition Metal ◽  
Transition Metal Catalysts ◽  
Cope Rearrangement ◽  
Biologically Relevant ◽  
The Past ◽  
Gold Silver ◽  
Dual Activation ◽  
Metal Catalyzed ◽  
Palladium Platinum

A (4+3)-cycloaddition combines a four-atom synthon and three-atom synthon to form seven-membered rings. In the past decade, many improvements have been made to this class of cycloaddition, including excellent diastereo- and enantioselectivities, both intra- and intermolecularly. Through the strategic use of transition-metal catalysts, acids, bases, and organocatalysts, it is possible to perform the cycloaddition on a variety of substrates, generating novel seven-membered rings. With these advances, (4+3)-cycloaddition has also been applied to the synthesis of biologically relevant compounds and natural products. We exclude the cycloadditions of cyclic dienes such as furan, pyrrole, cyclohexadiene or cyclopentadiene as Chiu, Harmata, Mascareñas­ and others have recently published thorough reviews on that topic. We will however discuss the recent additions (2009–2020) to the literature for the (4+3)-cycloadditions involving other types of four-atom synthons.1 Introduction2 Rhodium2.1 Cyclopropanation/Cope Rearrangement2.2 C–H activation3 Gold, Silver4 Copper5 Palladium, Platinum, Iridium6 Dual-Activation7 Conclusion

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