Synthesis of 2‐Aryl‐5‐oxo‐4‐[2‐(phenylmethylidene)hydrazino]‐2,5‐dihydro‐1H‐pyrrole‐3‐carboxylates by the Reaction between Hydrazones,Acetylenedicarboxylates, and 1‐Aryl‐N,N′‐bis(arylmethylidene)methanediamines

An efficient approach for the preparation of functionalized 2‐aryl‐2,5‐dihydro‐5‐oxo‐4‐[2‐(phenylmethylidene)hydrazino]‐1H‐pyrroles is described. The four‐component reaction between aldehydes, NH₂NH₂?H₂O, dialkyl acetylenedicarboxylates, and 1‐aryl‐N,N′‐bis(arylmethylidene)methanediamines proceeds in EtOH under reflux in good‐to‐excellent yields (Scheme 1). The structures of 4 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS, and, in the case of 4f , by X‐ray crystallography). A plausible mechanism for this type of reaction is proposed (Scheme 2).     

Surprising Formation of Chlorinated Butenolides from Dialkyl Acetylenedicarboxylates and Hexachloro­acetone in the Presence of Triphenyl Phosphite

Triphenyl phosphite reacts smoothly with dialkyl acetylenedicarboxylates and hexachloroacetone to produce alkyl 2‐(dichloromethylene)‐2,5‐dihydro‐5‐oxo‐4‐(trichloromethyl)furan‐3‐carboxylates in good yields.     

Multicomponent Reactions of Furan‐2,3‐diones: Synthesis and Characterizations of Furo[3,2‐c]pyran‐4‐ones

Furo[3,2‐c]pyran‐4‐ones, which possess a natural‐product skeleton, are synthesized via a simple, one‐pot, three‐component reaction of furan‐2,3‐diones with dialkyl acetylenedicarboxylates and Ph₃P.     

Excursion to the World of Heptacyclic Compounds Made of Azulenes and Acetylenedicarboxylates

Azulenes and acetylenedicarboxylates react under acid catalysis (Brønsted or Lewis) and form (2aRS,8aSR)‐2a,8a‐dihydrocyclopenta[cd]azulene‐1,2‐dicarboxylates as intermediate products, which then dimerize by central bond‐formation between C(2a¹) and C(2′a¹) and various peripheral C,C′‐atoms of the dihydroazulene fragments, depending on the substituents present. The reactions are often accompanied by the formation of side‐products, such as 2‐(azulen‐1‐yl)fumarates and ‐maleates and others caused by H‐shifts of the primary intermediates. H‐Shifts between the two tetrahydrocyclopenta[cd]azulene parts of the heptacyclic structures were also found.     

Reaction of N-Heterocycles with Acetylenedicarboxylates in the Presence of N-Alkylisatins or Ninhydrin. Efficient Synthesis of Spiro Compounds

Summary. The 1,3-dipolar intermediates generated by addition of isoquinoline, to dialkyl acetylenedicaboxylates are trapped by N-alkylisatins to produce dialkyl 1,2-dihydro-2-oxo-1-alkylspiro[3H-indol-3,2′-[2H,11bH][1,3]oxazino[2,3-a]isoquinoline]-3′,4′-dicarboxylates in excellent yields. The reaction of isoquinoline, quinoline, or pyridine with dimethyl acetylenedicarboxylate in the presence of ninhydrin led to dimethyl 1,2-dihydro-1,3-dioxospiro[3H-indene-3,2′-[2H,11bH][1,3]oxazino[2,3-a]isoquinoline]-3′,4′-dicarboxylate, dimethyl 1,2-dihydro-1,3-dioxospiro[3H-indene-3,3′[3H,4aH][1,3]oxazino[3,2-a]quinoline]-1,2-dicarboxylate, or dimethyl 1,2-dihydro-1,3-dioxospiro[3H-indene-3,2′-[2H,9aH]pyrido[2,1-b][1,3]oxazino]-3,4-dicarboxylate.     

Diastereoselective one-pot synthesis of novel ABCD-fused chromeno[2,3-d]pyrazolo[3,4-b]pyridines

A new aspect concerning chromone chemistry leading to the one-pot synthesis of functionalized novel ABCD-fused chromenopyrazolopyridines has been described. The synthesis involves a multicomponent reaction of chromone-3-benzoylhydrazones with isocyanides and acetylenedicarboxylates, whereupon novel complex tetracyclic benzopyrone derivatives containing three stereogenic centres were formed. The structure elucidation of the products was accomplished by 1D and 2D NMR experiments and confirmed by X-ray crystallographic analysis. Full assignment of all ¹H and ¹³C NMR chemical shifts has been unambiguously achieved. The reaction mechanism is also discussed. In addition, eight chromenopyrazolopyridine derivatives were tested for possible biological activity (antioxidant and lipid peroxidation inhibition).     

PbADC and PbADC·H2O: Two Coordination Polymers with Acetylenedicarboxylate (ADC2–) as Bridging Ligand

Single crystals of PbADC ( 1 ) and PbADC · H₂O ( 2 ) formed at the phase boundary of an aqueous silica gel containing acetylenedicarboxylic acid (HOOC–C≡C–COOH, H₂ADC) and an aqueous solution containing Pb(NO₃)₂. By choosing different concentrations of Pb(NO₃)₂, compounds 1 and 2 were obtained as phase pure products. Additionally, 1 was obtained by grinding Pb(CH₃COO)₂ · 3H₂O with H₂ADC resulting in a polycrystalline sample. The crystal structures of 1 (I4₁/amd, Z = 4; SrADC type structure) and 2 (P2₁/c, Z = 4, new structure type) were solved and refined from X‐ray single crystal data. Compound 1 exhibits a three‐dimensional framework structure: lead cations with a diamond‐like arrangement are interconnected by bridging ADC^2– ligands. In 2 double‐layers are formed by lead cations, bridging ADC^2– anions, and water molecules. These layers are held together by hydrogen bonds through water molecules and oxygen atoms of the ADC^2– ligands. Suspending 1 for 24 h in water at ambient conditions leads to the formation of 2 , which can be converted to 1 again by careful dehydration at approx. 400 K in vacuo. This reversible reaction can be structurally interpreted as a topochemical reaction, which transforms a 3D coordination network into a 2D network structure and vice versa, as both crystal structures show noticeable structural similarities.     

Multicomponent Transformation of Isoindoline‐1,3‐diimine (=1H‐Isoindole‐1,3(2H)‐diimine), Acetylenic Esters,and Triphenylphosphine to Novel Dihydropyrimido[2,1‐a]isoindole Derivatives

The three‐component reaction of the zwitterions generated from dialkyl acetylenedicarboxylates (=dialkyl but‐2‐ynedioates and triphenylphosphine (Ph₃P) with isoindoline‐1,3‐diimine (=1H‐isoindole‐1,3(2H)‐diimine) is described (Scheme 1). This reaction affords the corresponding special type of substituted dihydropyrimido[2,1‐a]isoindole derivatives in good yields without using any catalyst and activation (Table).     

Expeditious one-pot synthesis of highly substituted thiazolo[3,2-a]pyridines involving chromones

The 1,4-zwitterion derived from 4,5-dimethylthiazole and acetylenedicarboxylates has been shown to react at low temperature readily with 3-formylchromones (chromone-3-carboxaldehydes) resulting, after an unusual rearrangement, in the facile synthesis of thiazolo[3,2-a]pyridine derivatives; in the case of electron-donating substituents in the chromone ring tetracyclic chromenothiazolopyridines are isolated as the main reaction products. However, at higher temperature after an unexpected 1,2-aroyl migration 8-formyl-5H-[1,3]thiazolo[3,2-a]pyridines are formed as a mixture of two rotamers. Structural assignments of the new compounds as well as complete assignment of ¹H and ¹³C NMR signals were based on the analysis of their ¹H and ¹³C NMR (1D and 2D), IR, MS and elemental analysis data. Plausible mechanisms are proposed.