Huisgen [3 + 2] Dipolar Cycloadditions of Phthalazinium Ylides to Activated Symmetric and Non-Symmetric Alkynes

Abstract

We present herein a straightforward and efficient pathway for the synthesis of pyrrolophthalazine cycloadducts via Huisgen [3 + 2] dipolar cycloaddition reactions of phthalazinium ylides to methyl propiolate or dimethyl acetylenedicarboxylate (DMAD). A thoroughly comparative study concerning the efficiency of synthesis, conventional thermal heating (TH) versus microwave (MW) and ultrasound (US) irradiation, has been performed. The cycloaddition reactions of phthalazinium ylides to methyl propiolate occur regiospecific, with a single regioisomer being obtained. Under conventional TH, the cycloaddition reaction of phthalazinium ylides with DMAD occurs to a mixture of inseparable partial and fully aromatized pyrrolophthalazine cycloadducts, while MW or US irradiation are leading only to fully aromatized compounds, with the reactions becoming selective. A feasible mechanism for formation of fully aromatized compounds is presented. Besides selectivity, it has to be noticed that the reaction setup under MW or US irradiation offer a number of other certain advantages: higher yields, decreasing of the amount of used solvent comparative with TH, decreasing of the reaction time from hours to minutes and decreasing of the consumed energy; consequently, these reactions could be considered environmentally friendly.

Fluorescent Azasteroids through Ultrasound Assisted Cycloaddition Reactions

“…In recent years, ultrasound-assisted reactions have proved to be a new versatile tool in synthetic organic chemistry [ 18 , 19 ], offering a facile and usefully alternative in a large variety of syntheses [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. In comparison with conventional thermal heating (TH), ultrasound irradiation has several important advantages in terms of higher yields, increased purity of the compounds and selectivity, shorter reaction times, lower costs, and simplicity in handling and processing.…”

“…In comparison with conventional thermal heating (TH), ultrasound irradiation has several important advantages in terms of higher yields, increased purity of the compounds and selectivity, shorter reaction times, lower costs, and simplicity in handling and processing. All these advantages make US-assisted reactions environmentally friendly [ 22 , 23 , 24 , 28 ].…”

“…A special focusing was paid to the dipolar cycloaddition reactions of azinium ylides with various dipolarophiles in order to obtain new compounds with blue-fluorescent properties. Herein, we add further contributions in the field of using US irradiation in organic chemistry [ 20 , 21 , 22 , 23 , 24 ] and propose a facile, efficient, and environmentally friendly method for the synthesis of blue-emitting derivatives using US technologies.…”

Synthesis of 1-(2-Fluorophenyl)pyrazoles by 1,3-Dipolar Cycloaddition of the Corresponding Sydnones

“…The 1,3-dipolar cycloadditions reactions [ 1 ], also known as “Huisgen reactions” [ 2 ], involving 1,3-dipoles from the class of N -ylides [ 3 , 4 , 5 , 6 ], mesoionic compounds such as munchnones [ 7 , 8 ] and sydnones [ 9 , 10 ] and many others [ 11 , 12 ], have been intensively studied in obtaining a wide range of five membered heterocycles ( Figure 1 ) [ 13 ].…”

Hybrid Pyridine Bis-Anthracene-Imidazolium Salt: NMR Studies on Zn-Acetate Complexation

“…Considering our experience in the field of the synthesis of hybrid compounds with imidazole/benzimidazole, pyridine and anthracene units [2,[6][7][8][9][10][11], and our previous experience in the area of cycloimonium ylides [12][13][14][15][16][17][18][19][20][21][22], we decided to synthesize a novel hybrid pyridine bis-anthracene-imidazolium salt, and also to study its complexation to Zn acetate by NMR.…”