An improved preparation of tetrahydropyridines from 1-alkyl-3-acylpyridinium salts

The hydrogenation of 1-alkyl-3-acylpyridinium salts in methanol in the presence of 10% palladium-charcoal/disodium hydrogen phosphate-sodium dihydrogenphosphate suspension leads to the corresponding tetrahydropyridines. This represents an improvement over the Wenkert method.     

Palladium-Assisted Heteroannulation of Acetoxy-1, 3-dienes

The reaction of organomercurials 1, 2, or 3, LiPdCl₃ and acetoxy-1, 3-dienes affords good yields of the corresponding 2, 3-dihydrobenzofurans, 3, 4-dihydroisocoumarins and α-methylene butyrolactones respectively with interesting regioselectivity.     

Recyclization of 1-amino-3.5-diaryl-2.6,6-tricyanocyclohexa-1,3,-dienes to pyridine derivatives

The base-catalyzed recyclization of 1-amino-3,5-diaryl-2,6, 6-tricyanocyclohexa-1,3-dienes to 2,4-diaryl-5-cyano-6-dicyanomethylene-1,2,3,6-tetrahydropyridines, 4,6-diaryl-3-cyano-2-dicyanomethylene-1,2-dihydropyridines, and 4,6-diaryl-3-cyano-2-dicyanomethylpyridines has been investigated. The intermediate products of this reaction — cis, trans-2-amino,4,6-diaryl-1,1,3-tricyanohexa-1,3,5-trienes —have been isolated; on heating these are transformed reversibly into the initial cyclohexadienes or they isomerize irreversibly into trans, trans-hexatrienes, while in the presence of a base (piperidine, diethylamine, triethylamine, KOH), they cyclize to form the above-mentioned' pyridine derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, PP. 621–625, May, 1986.     

A facile method for the stereoselective preparation of (1E,3E)-4-substituted-1-amino-1,3-dienes via 1,4-elimination

The 1,4-elimination reaction of 1-amino-4-methoxy-(2Z)-alkenes is shown to proceed with high (1E,3E)-stereoselectivities to afford the corresponding 4-substituted-1-amino-1,3-dienes in good yield. The scope and stereochemical features of the synthetic method are described.     

An improved protocol for the Prins desymmetrisation of cyclohexa-1,4-dienes

Improved conditions are reported for the Prins-pinacol rearrangement of cyclohexa-1,4-diene-derived acetals. The use of triflic acid gives particularly clean reaction, resulting in a mixture of regioisomers in an approximately 10:1 ratio. A tethered version of this reaction is also reported, giving a tricyclic compound with the same stereochemistry as the core of the cladiellin diterpenes.     

Intermolecular diels-alder reactions of n-acyl-n-alkyl(aryl)-1-amino-1,3-dienes

Intermolecular Diels-Alder additions of the readily available dienamides $\text{3}$ to various dienophiles proceeded in a regio- and stereoselective manner, allowing the preparation of complex anilides ($\text{5}$), cyclohexenyl amides ($\text{6}$, $\text{8}$) and bridged heterocycles ($\text{13}$).     

An efficient procedure for the preparation of (1S,3R)- and (1S,3S)-1-amino-3-(hydroxymethyl)cyclopentanes

Enantiomerically pure (1S,3S)- and (1S,3R)-1-amino-3-(hydroxymethyl)cyclopentanes have been efficiently synthesized from L-aspartic acid. The title compounds are isosteres of ribose and may be used to construct nucleoside analogs with important antiviral and antineoplastic activities as demonstrated by a concise total synthesis of (+)-4'-deoxycarbapentostatin nucleoside.     

A new and versatile method for iodofunctionalization of 1,3-dienes

We wish to report the reactions of conjugated dienes with I(py)₂BF₄. This simple and general method allows the regiospecific 1,2-addition of iodine and a nucleophile to terminal dienes and the 1,4-addition to internal dienes.     

Lipase catalysis in the preparation of 3-(1-amino-3-butenyl)pyridine enantiomers

The kinetic resolution of 1-(3-pyridyl)buten-3-ylamine with activated and non-activated acyl donors and Burkholderia cepacia lipase (lipase PS-D) under dry conditions has been studied. The N-acylation in isopropyl acetate (E >100) and the acidic hydrolysis of the (R)-amide produced gave the corresponding enantiomerically enriched amines.     

Studies on pyrazines, 8. An improved syntheses of 2-amino-3,5-dibromo- and 2-amino-5-bromopyrazines

The titled dibromopyrazine ( 2 ) was prepared in 54% yield by the modified procedure for bromination of 2-aminopyrazine ( 1 ) using bromine and pyridine in chloroform solution. Similarly, 2-amino-5-bromopyrazine ( 3 ) was directly prepared in 36% yield by bromination using 1.2 equivalents of the above reagents.     

An improved and facile synthesis of 2-amino-1,1,3-tricyanopropene

A simple method for the dimerization of malononitrile using alkali hydroxides in methanol or ethanol is described. Thereby 2-Amino-1,1,3-tricyanopropene, a keyintermediate for heterocyclic chemistry, is obtained in high yield.

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Eine verbesserte und bequeme Synthese von 2-Amino-1,1,3-tricyan-propen (Kurze Mitteilung)

Zusammenfassung Eine einfache Dimerisierung von Malononitril unter Verwendung von Alkalihydroxid in Methanol und Ethanol wird beschrieben. Dabei entsteht in guter Ausbeute 2-Amino-1,1,3-tricyan-propen, ein wichtiges Ausgangsprodukt zur Synthese von Heterocyclen.

     

Diels-alder reactivity of 1-alkoxyphenyl-3-trialkylsiloxy-1,3-dienes

The synthesis of 1-(3,4,5-trimethoxyphenyl)-3-trialkylsiloxy-1,3-butadienes and their Diels-Alder reaction with selected dienophiles at room temperature is described. These aryldienes are useful building blocks for the synthesis of natural and pharmacological active products, as has been shown by the preparation of a tetracyclic ketone needed for the synthesis of new anthracycline analogues.