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N,N,N-Heterocycles
Published in Navjeet Kaur, Metals and Non-Metals, 2020
Triazoles can be synthesized efficiently by azide-alkyne Huisgen [3+2]-cycloaddition reaction, better known as the ‘click’ reaction [118]. These reactions catalyzed by copper(I) or copper(II) species and performed at slightly elevated or ambient temperatures take several hours for completion. Although limited in number, there have been reports of such cycloaddition reactions being catalyzed by heterogeneous catalysts. Lipshutz and Taft [119] synthesized 1,2,3-triazoles using charcoal-supported Cu (copper/carbon) as a highly regioselective and robust heterogeneous catalyst. The reaction required 1 eq. of base such as Et3N under traditional heating conditions to ensure high reaction rates. However, under MW irradiation, the reaction was performed quantitatively within 3 minutes at 150 °C without any external base or ligand. The Huisgen [3+2]-cycloaddition can be carried out under MWI using a ligand/additive-free copper-manganese bimetallic heterogeneous catalyst as well (Scheme 64) [120]. For this, the optimum ratio of manganese:copper has been found to be 0.25:2. This click reaction produces 1,4-disubstituted 1,2,3-triazoles in quantitative yields from a variety of substrates under MW-assisted conditions and, after the reaction, the catalyst is easily removed by filtration and reused up to nine times without significant loss of activity [121].
A Review on the Selective Synthesis of Spiro Heterocycles Through 1,3-Dipolar Cycloaddition Reactions of Azomethine Ylides
Published in Tanmoy Chakraborty, Lalita Ledwani, Research Methodology in Chemical Sciences, 2017
Anshu Dandia, Sukhbeer Kumari, Shuchi Maheshwari, Pragya Soni
Cycloaddition reactions are one of the most important classes of reactions in synthetic chemistry.1 Within this class, the 1,3-dipolar cycloaddition reaction has found extensive use as a high-yielding regio- and stereocontrolled method for the synthesis of different heterocyclic compounds.2 Indeed, the 1,3-dipolar cycloaddition reaction has been described as “the single most important method for the construction of heterocyclic five-membered rings in organic chemistry.”3 Integrating the ylide (dipole) and the alkene or alkyne (dipolarophile) within the same molecule provides direct access to bicyclic (or polycyclic) products of considerable complexity. The proximity of the reactants and the conformational constraints often lead to ready cycloaddition with very high or complete selectivity.
Conjugation and Reactions of Conjugated Compounds
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
A cycloaddition reaction involves a molecule containing a π-bond (an alkene, alkyne, etc.) and a 1,3-dipole. It is a chemical reaction between a 1,3-dipole an a dipolarophile to form a five-membered ring. Is there an intermediate in the [3+2]-cycloaddition reaction?
Effect of ϒ- irradiation and study of ϒ-induced physico-chemical changes in high performance thermoset obtained by double cycloaddition of munchnone and bis-maleimide
Published in Radiation Effects and Defects in Solids, 2020
Balakrishna Kalluraya, B. R. Kaushik, T. Vishwanath, H. M. Somashekarappa
Mesoionic compounds have been known for many years and have been extensively utilized as substrates in 1,3-dipolar cycloaddition (1–5). Of the known mesoionic heterocycles, munchnones have generated considerable interest in recent years (6–9). Munchnones are readily prepared by cyclodehydration of N-acyl amino acid (1) with reagents such as acetic anhydride (1–3). The reaction of munchnones with acetylenic dipolarophiles results in the formation of pyrrole derivative (10–17). Cycloaddition studies of munchnones with other dipolarophiles have resulted in practical, unique syntheses of numerous functionalized monocyclic and ring annulated heterocycles (1–3). The development of novel and effective approaches for the synthesis of bridged heterocyclic ring systems is an important area in organic synthesis (18). Intramolecular 1,3-dipolar cycloaddition offers a potent methodology for the formation of such bridged heterocyclic compounds (19).
Synthesis of conjoined 1,5-dithiaspiro derivatives through catalyst free double reaction of carbon disulfide with dialkyl acetylenedicarboxylates and isocyanide derivatives
Published in Journal of Sulfur Chemistry, 2018
Amirhossein Khooshehchin, Hamidreza Safaei
Recently, the Wang group reported dual 1,3-dipolar cycloaddition of CO2 with isocyanides and dialkyl acetylenedicarboxylates that utilize both C = O bonds of CO2 in one reaction. Their finding of a double reaction of CO2 molecule [29], the similar reactivity and chemistry of CO2 and CS2 [30], and our experiences and expertise in isocyanide [31] and carbon disulfide [32] chemistry encouraged us to develop a dual reaction using both carbon–sulfur double bonds in CS2. Herein, we report a facile and catalyst free dual 1,3-dipolar cycloaddition of CS2 with isocyanides and dialkyl acetylenedicarboxylates. To the best of our knowledge, this is the first report that both C = S bonds of CS2 react in one reaction and become incorporated into clinging twin spiro hetero-sulfur cyclic compounds. The reaction is performed at 70°C and under solvent-less conditions (Scheme 2).
Construction of polymeric Cu(I) N-heterocyclic carbene complex utilizing terpyridine-Fe(II) as linkers: formation of an efficient and recyclable catalyst
Published in Journal of Coordination Chemistry, 2018
To further investigate the scope of this catalyst recycling procedure, a second copper(I)-catalyzed reaction, Huisgen 1,3-dipolar cycloaddition reaction was performed. For this reaction, the [Tpy-FeII-NHC-CuI] catalyst was proved to be well-suited for the cycloaddition reaction and the desired product was isolated in 93% yield under the optimized conditions. To examine the scope of the reaction, the reaction of phenylethyne with different azides was first tested under solvent-free conditions. The results indicated that benzyl azides and aromatic azides with both electron-donating and electron-withdrawing functionalities gave high yields of the products (Table 3, entries 1–5). However, the reactions of alkyl azides with phenylacetylene led to slower reactions and needed a prolonged reaction time (entries 6 and 7). Subsequently, a variety of alkynes were also examined by using benzyl azide-terminal alkynes combination (entries 8–12). As it can be seen from Table 3, the reactivity of aliphatic and aromatic alkynes was all observed, in which aromatic alkynes were often much more reactive than aliphatic alkynes.