Zur reaktion von cyclopropenonen mit azomethinen V reaktionen von diphenylcyclopropenon mit N.N.N′.N′-tetraalkylguanidinen unb benzamidinen

Reaction of Amidrazones with 2,3-Diphenylcyclopropenone: Synthesis of 3-(aryl)-2,5,6-Triphenylpyrimidin-4(3H)-ones

“…Interestingly, the product formation excluded the formal [2 + 3] cycloaddition pathways proposed by Eicher. [8][9][10][11][12][13] The reaction mechanism can be simply described as due to the hydrazine addition to C-2 of 1 leading to intermediate 6. Thereafter amidine-like reaction of N-3 to the carbonyl might occur to form salt 7 (Scheme 3).…”

“…6,7 2,3-Diphenylcyclopropenone (1) has been found to react with a wide range of imines and other compounds containing the C=N moiety, usually to form azacyclopentenones (pyrrolinones) via formal [2π + 3π] cycloaddition reactions. [8][9][10][11][12][13] In contrast, the reaction of 1 with guanidine and its alkyl and/or aryl derivatives gives the corresponding 5,6-dihydropyrimidin-4(1H)-ones via a formal [3π + 3π] cycloaddition reaction. 14 In general, cyclopropenones are strained ring ambident electrophiles with a tendency to form ring-opened products; their reaction with nucleophiles can involve carbonyl or conjugate addition.…”

Non‐Aromatic 3H‐Pyrroles in the Reaction with Nucleophiles: Is High Reactivity a Myth?

“…Substitution of chlorine atom in 2‐chloro‐3 H ‐pyrroles under the action of pyrrolidine or potassium hydrosulfide was assumed to proceed in a stepwise manner through the addition of a nucleophile with further elimination of hydrogen chloride molecule (Scheme b). Also, the reversible addition of oxygen (methanol, ethanol) and nitrogen (dimethylamine, pyrrolidine, piperidine, morpholine) nucleophiles to the carbon–nitrogen double bond of 3 H ‐pyrroles with exo‐cyclic carbonyl function was reported (Scheme c) . Recently, formal [3+2] cycloaddition of allenoates to twofold excess of isocyanoacetates to form bicyclic imidazolines was discovered and proved to proceed through the addition of isocyanoacetates as carbon nucleophiles to the azadiene system of intermediate 3 H ‐pyrroles (Scheme d).…”

Unusual reactivity of thiosemicarbazides towards 2,3-diphenylcyclopropenone: synthesis of new pyridazinethiones and 1,2,4-triazolo[4,3-b]pyridazinethiones

“…8 Diphenylcyclopropenone (1) has been found to react with a wide range of imines and other compounds containing the C=N moiety, usually to form azacyclopentenones (pyrrolinones) via formal [2+3] cycloaddition reactions. [9][10][11][12][13][14] By contrast, the reaction of 1 with guanidine and its alkyl and/or aryl derivatives gave the corresponding 5,6-dihydro-4(1H)-pyrimidinone via a formal [3+3] cycloaddition reaction. 15 In general, cyclopropenone is amphiphilic, reacting readily with both nucleophilic and electrophilic reagents.…”

“…Moreover, cyclopropenones are strained ring ambident electrophiles with a tendency to form ring opened products, their reaction with nucleophiles has the possibility of carbonyl or conjugate addition. [9][10][11][12][13][14][15][16][17] Recently, we have found that the reactions of aroylphenylthioureas with 1 in acetic acid afforded the diasteromers of 3-(3 \ -aroyl-1-substituted-thioureido)-2,3-diphenylcinnamic acids. 18 Generally, the N 2 of thiosemicarbazides is described as a softer nucleophilic center than the harder and powerful terminal nitrogen N 1 .…”