Synthese von Pyrimido[1,2-a]benzimidazolen durch Umsetzung von 2-Aminobenzimidazol mit Acetylendicarbonsäure-dimethylester und ihre Überführung in Imidazo[1,2-a]benzimidazole

The main product of the reaction between 2-aminobenzimidazole and dimethyl acetylenedicarboxylate is shown to be methyl 1, 2-dihydro-2-oxo-pyrimido[1, 2-a]benzimidazole-4-carboxylate ( 6 ), which can be methylated at position 1 to give 7 . Catalytic hydrogenation of 7 leads to the 1,2,3,4-tetrahydro derivative 8 , whereas NaBH₄ reduces the ester and, to some extent, the double bond to yield a mixture of 9 and 10 . When a 1-substituted 1, 2-dihydro-4-hydroxymethyl-pyrimido[1, 2-a]benzimidazol-2-one (for example 11 ) is catalytically hydrogenated, the double bond is unaffected, but hydrogenolysis of the alcohol group occurs instead to give 13 . The lactam group is less stable in the tetrahydro series than in the dihydro compounds. For example, the lactam is cleaved when 8 is treated with amines containing a small amount of water, and the monoamides 16 and 17 are formed. Similarly, sodium hydroxyde cleaves the lactam under mild conditions to the dicarboxylic acid 19 , which can be converted to 2, 3-dihydro-1-methyl-2-oxo [1H]imidazo[1, 2-a]benzimidazole-3-acetic acid (4-methyl)piperazide ( 20 ) with thionyl chloride and N-methylpiperazine. However, when 7 is treated with methylamine at low temperature, the amide 22 is formed, whilst at room temperature the amine attacks both the ester and the double bond to give 23 . The structure of 8 was confirmed by X-ray analysis.     

Neue Spiroverbindungen aus Cyclophosphazenen und Cyclodi[phosphadiazan]en

New Spiro Compounds from Cyclophosphazenes and Cyclodi[phosphadiazanes] Chlorocyclophosphazenes (Cl₂P = N)₃ and (Cl₂p = N)₄ react with dihydrazidophosphoric acid derivatives in THF in the presence of triethylamine to give the spirocyclic compounds Cl₄N₃P₃(NHN(CH₃))₂P(S)OC₆H₅, Cl₆N₄P₄(NHNH)₂P(S)OC₆H₅. Constitutions have been confirmed by MS, NMR, IR and elemental analysis.     

Rhodium (I)-katalysierte Reaktionen der [2+4]-Cycloaddukte aus 3,4-Dimethoxyfuran und Acetylendicarbonsäure-estern

[2+4]-Cycloaddition Products of 3,4-Dimethoxyfuran with Acetylenedicarboxylates and Their Transformations under the Influence of Rhodium(I) Catalysts 3,4-Dimethoxyfuran ( 1 ) readily reacts with acetylenedicarboxylates ( 2 ) at room temperature in a [2+4]-cycloaddition to give a mono-( 3 ) and several di-addition products. 90% of the latter consists of the endo-exo compound 4 . Under the influence of catalytic amounts of [Rh(CO)₂Cl]₂ the mixture of mono- and di-adducts in methanolic solution is smoothly transformed into endo-5,5,6-trimethoxy-7-oxabicyclo [2.2.1]hept-2-ene-2,3-dicarboxylate

1 Alle Verbindungen sind racemisch. Die Formeln stellen jeweils nur ein Enantiomeres dar.

(5) , 3-hydroxy-4,5-dimethoxyphthalate ( 6 ) and (I R *, 2 S *, 4 R *, 5 R *, 7 R *, 11 R *, 12 R *) -5,8,8,9,12-pentamethoxy-3,6-dioxatetracyclo [5.3.1.1 ^2,5 . 0 ^4,11 ]dodec-9-ene-1,11-dicarboxylate ( 7 ).     

Reaktionen von 5H-1,2λ5-Azaphospholen mit Arylazocarbonitrilen sowie Acetylendicarbonsäure-estern

Reactions of 5H,2λ⁵-Azaphospholes with Arylazocarbonitriles and Dialkyl Acetylenedicarboxylates Azaphospholes 1a – c react with activated arylazocarbonitriles to 1,5,2λ⁵-diazaphosphorines 2a – c and 3a – c . The reaction of 1a – c with diethyl or dimethyl acetylenedicarboxyiates yields 7H-1,4λ⁵-azaphosphepines 4a – c . The structures of 2b , 3a , and 4a are established by an X-ray diffraction analysis.     

Cyclische Phosphorsäure- und Thiophosphorsäurederivate aus den Säuredihydraziden und bifunktionellen Siloxanen Neue anorganische Heterocyclen mit bis zu zehn Ringgliedern

Cyclic Derivatives of Phosphoric and Thiophosphoric Acid from the Corresponding Acid Dihydrazides and Bifunctional Siloxanes. New Inorganic Heterocycles with up to Ten Ring Members Dihydrazidophosphoric and dihydrazidothiophosphoric acid phenylester react with α, Ω-dichloroorganodisiloxanes and -trisiloxanes in the presence of triethylamine as a base yielding ring compounds. With dichlorotetraphenyldisiloxane a six-membered ring with two exocyclic NH₂ groups, a seven-membered ring with only one exocyclic NH₂ group and an eight-membered ring without such groups are formed. With dichlorohexamethyltrisiloxane corresponding mixtures of eight-, nine-, and ten-membered rings are obtained. Five new ring compounds could be isolated as pure isomers by fractional crystallization and have been characterized by analysis and spectroscopic methods.     

Zur Reaktionsweise von Diphenylcyclopropenon mit β-Carbonyl-enolaten. I. Einsatz von Acetylaceton,Acetessigsäure-methylester, 2-Äthoxycarbonyl-cyclododecanon und Malonsäure-dimethylester

Reaction of Diphenylcyclopropenone with β-Carbonyl-enolates. I. Use of Acetylacetone, Methyl Acetoacetate, 2-Ethoxycarbonyl-cyclododecanone and Dimethyl Malonate The reaction of the sodium salts of acetylacetone ( 6 ), methyl acetoacetate (7) , 2-ethoxycarbonyl-cyclododecanone (8) , dimethyl malonate (19) and its methyl derivative 20 with diphenylcyclopropenone ( 5 ) in dimethylformamide at room temperature led to the unsaturated γ-lactones 14, 15, 17, 22 and 36 . In the case of dimethyl malonate ( 19 ), the halfester 21 , the acyl-malonic ester 24 and the indenone-malonic ester 23 were also isolated. Several intermediates and the final products were characterised by reactions and spectroscopically. A general mechanism is discussed for the addition of cyclo-propenones ( 1 ) to the enolate salts of β-dicarbonyl compounds 4 involving the bicyclic lactone-enolates 18 and 32 as intermediates. The products formed via 18 and 32 are considered to be the result of an attack of one of the oxygen atoms of the β-carbonyl-enolate anion ( 4 ), the product 24 , on the other hand, of the attack of the α-carbon atom of 4 ; in both cases the attack is on the carbonyl C-atom of 5 .