Zur Reaktion von Cyclopropenonen mit Azomethinen, VIII Diphenylcyclopropenon und cyclische Imine

Copper-catalyzed condensation of imines and α-diazo-β-dicarbonyl compounds: modular and regiocontrolled synthesis of multisubstituted pyrroles

“…The reaction of the former imine successfully furnished the desired pyrrole scaffold 3aaf in 62% yield ( Scheme 5a ). By contrast, the latter exclusively afforded a dihydrobenz[ g ]indolizinone derivative 6 , 16 the structure of which was unambiguously confirmed by X-ray crystallographic analysis ( Scheme 5b ).…”

“…9b – c Interestingly, the benzyl-substituted dihydroisoquinoline 1ab afforded a mixture of 5,6-dihydropyrrolo[2,1- a ]isoquinoline 3aba and an unexpected dihydrobenz[ g ]indolizinone derivative 3aba′ . 16 The latter product features the migration of the phenyl group of 1ab from the β-position of the nitrogen atom to the α-position, as well as the concomitant oxidation of the β-position. We consider that these structural changes occur on the reaction pathway leading to the pyrrole product 3aba , rather than after the formation of 3aba , because the ratio of 3aba and 3aba′ was not affected by the reaction time (see Scheme S1 in the ESI † for a possible mechanism).…”

Protic‐Solvent‐Mediated Cycloisomerization of Quinoline and Isoquinoline Propargylic Alcohols: Syntheses of (±)‐3‐Demethoxyerythratidinone and (±)‐Cocculidine

“…Surprisingly, the benzindolizinone framework has gone virtually unexplored: only scattered reports of benz[ e ]indolizinones3 and only a single report of the isomeric benz[ g ]indolizinone4 had appeared prior to the study that is described herein. To demonstrate the utility of the unique azacyclic products that can now be effectively accessed by the protic‐solvent‐mediated cycloisomerization, we applied the benz[ g ]indolizinone scaffold to short syntheses of the Erythrina alkaloids5 (±)‐3‐demethoxyerythratidinone ( 4 )6 and (±)‐cocculidine ( 5 ) 7…”

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 .…”