Heterocycles. Part I. A new route to the synthesis of substituted 2-aminopyrimidines

Heterocyclic aldehydes (A) reacted with alkyl aryl ketones (B) to give the corresponding 1,3-diaryl-2-propen-1-ones (Ia-1). Condensation of these chalcones with guanidine produced the corresponding 2-amino-4,6-diarylpyrimidines (IIa-1). The structure of all products was substantiated by chemical and spectroscopic methods.     

A new synthetic approach to the bicyclo[5.3.1]undecane ring system in taxanes

The bicyclo[5.3.1]undecane derivative 19, which was referred to the A,b ring system of taxane diterpenes, was synthesized by a base-induced fragmentation reaction of the tricyclic diol monomesylate 18 derived highly stereoselectively from 5-methyl-1,3-cyclohexadione.     

A new synthetic approach towards 7-substituted 2-alkyl-2,3,4,9-tetrahydro-1H-fluorenes

Cyclization of 2-(4-bromophenyl)-5-pentylcyclohex-1-ene-1-carboxylic acid followed by reduction of the carbonyl group resulted in the corresponding 7-substituted derivative of 2-alkyl-2,3,4,9-tetrahydro-1H-fluorene.     

A new synthetic approach to the C-D ring portion of streptonigrin analogues

Development of an efficient synthesis of the C-D ring portion of streptonigrin is a key operation in the synthesis of this antibiotic and its analogues. A new method for the synthesis of 3-cyano-5,6-dimethyl-4-(3,4,5-trimethoxyphenyl)-2-pyridone ( 14 ), a compound having the requisite functionality for conversion into a streptonigrin analogue, has been established. It involves treatment of 3,4,5-trimethoxybenzonitrile with ethylmagnesium bromide and malononitrile to give propylenemalononitrile derivative 7 , which is condensed with trimethyl orthoacetate to give a mixture of 9 and pyridine derivative 12 . Demethylation of 12 then affords 14 . The overall yield for this route was 50%, allowing for conversion of 9 to 12 .     

A ring closing metathesis approach to the indole alkaloid mitralactonine

An efficient utilisation of RCM leading to a convenient synthesis of a pentacyclic indole alkaloid is described.     

A palladium-catalyzed synthetic approach to new Huperzine A analogues modified at the pyridone ring

The synthesis of two new Huperzine A analogues is reported. Both products present an amino substituted benzo-fused system in place of the pyridone ring of the natural alkaloid. The synthetic strategy to the two analogues is based on three different key palladium-catalyzed steps, namely a carbonylation reaction, an epoxide isomerization and a bicycloannulation reaction.     

A new synthetic approach to the benzazole ring system. Synthesis and electrocyclic ring closure of dialkenyl and alkenyl-aryl substituted pyrroles,imidazoles and oxazoles

An efficient synthesis is described of the substituted azoles referred to in the title, which are precursors of an equally successful new synthetic approach to indoles, benzimidazoles and benzoxazoles.     

吲哚环化合物合成方法的进展

综述了在工业、农业和医药等领域中有着广泛重要用途的吲哚环化合物近二十年以来合成方法上的进展。     

Heterocycles. Part X. Synthesis of new pyrimidine systems

Selected aryl aldehydes I were reacted with 1-benzosuberone to give the corresponding 2-arylidene-1-ben-zosuberones II. Condensation of these chalcones with urea and thiourea revealed the formation of the corresponding substituted pyrimidin-2-ones III , and pyrimidine-2-thiones IV respectively. The structure of all products was substantiated by chemical and spectral methods.     

A synthetic approach to taxane diterpenes. A synthesis of the bicyclo[5.3.1]undecenone ring system

Bicyclo[5.3.1]undecenone 2 corresponding to A and B rings in taxane diterpenes was synthesized. The eight-membered ring was constructed by a base-induced intramolecular cyclization of twelve-membered lactam sulfoxides 15.     

A new synthetic approach to phenothiazine-2-amines

Elaboration of a Buchwald-Hartwig protocol for the introduction of amino functions to position 2 of the phenothiazine ring system has opened a new access to various N-alkyl and N-dienyl phenothiazines bearing secondary amines, tertiary amines, and amide moieties. Hydrolysis of the amido derivatives gave unsubstituted phenothiazine-2-amines. This protocol provides an easy access to phenothiazine-2-amines starting from the commercially available starting compounds.     

Reactivity of 4-bromomethylquinoline derivatives towards glycine and thioglycolic acid. A new ring system

Condensation of 4-bromomethylquinoline derivatives1 a-1 c with glycine and thioglycolic acid gave the corresponding quinolylmethylglycine and quinolylmethylthioacetic acid derivatives2 a-2 c and2 d-2 f, respectively. Cyclization of2 a-2 f was affected either by polyphosphoric acid or concentrated sulphuric acid to give3 a-3 f. Chlorination of2 a-2 f and3 a-3 f were also accomplished.

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Die Reaktivität von 4-Brommethylchinolin-Derivaten gegenüber Glycin und Thioglycolsäure. Ein neues Ringsystem

Zusammenfassung Die Reaktion von 4-Brommethylchinolin-Derivaten1 a-c mit Glycin und Thioglycolsäure gab die entsprechenden Kondensationsprodukte2 a-c und2d-f.2 a-f konnten mit Polyphosphorsäure bzw. mit konzentrierter Schwefelsäure zu Benzo[c]-2,6-naphthyridinen3 a-f zyklisiert werden.2 a-f und3 a-f waren einer Chlorierung (POCl₃) zugängig.

     

Dimeric indole alkaloids of a new type a synthetic approach to the ervafoline series

A synthetic approach towards the dimeric ervafoline indole alkaloids has been achieved $\text{via}$ a route inspired from a biogenetic hypothesis.     

An efficient synthetic approach towards new 5, 5'-diaryl-2, 2'-bipyridine-based fluorophores

An efficient approach has been developed for the synthesis of 5,5'-diaryl-2,2'-bipyridines via their 1,2,4-triazine analogues. The notable advantages of the present method are:The possibility of varying the aromatic substituents in the positions 5 and 5' of bipyridine core and the possibility for obtaining 2,2'-bipyridines bearing a fused cyclopentene core to increase the solubility in organic solvents. These 5,5'-diaryl-2,2'-bipyridines exhibited an intense emission in a range of ca. 422-521 nm in acetonitrile solution; depending on the nature of the aromatic substituents and the presence of annulated cyclopentene fragments. Apart from that, the significant bathochromic shifts of the both absorption and emission maxima were observed in comparison with a number of previously described similar structures. In some cases the significant increasing of the fluorescence quantum yields took place.     

Synthesis of 4H-furo[3,2-b]indole derivatives A new heterocyclic ring system

4H-Furo[3,2-b]indole (III) was prepared from deoxygenation of 2-(2-nitrophenyl)furan (II) with triethyl phosphite and thermolysis of 2-(2-azidophenyl)furan (VI). 4H- or 4-alkylfuro [3,2-b]indole-2-carboxaldehydes (VIII, IXa-c) were obtained by Vilsmeier formylation of the corresponding furo[3,2-b]indoles (III, VIIa-c). 4H-Furo[3,2-b]indole-2-carboxaldehyde (VIII) was submitted to the Cannizzaro, Wittig and reduction reactions. The Shiff's bases were obtained by the reaction of 4-ethylfuro[3,2-b]indole-2-carboxaldehyde (IXb) with amines. J. Heterocyclic Chem., 14, 975 (1977)     

A novel synthetic approach towards 2-guanidinomethyl-4(5)-sulfamoylimidazoles

A library of 2-guanidinomethyl-4(5)-sulfamoylimidazoles was synthesised in a convergent manner by introducing a sulfonyl chloride group via a trianion electrophilic sulfinylation of suitably protected 2-guanidinomethyl imidazoles.     

A new synthetic approach to the C ring of known as well as novel bryostatin analogues

[reaction: see text] A new approach to the synthesis of the C ring subunit of known and potential bryostatin analogues is described. The convergent approach, illustrated above, requires fewer steps and offers greater flexibility in rapidly accessing diverse C ring analogues.     

A new synthetic approach towards isoquinobenzazepinone and isoindolinobenzazepinone using acid-mediated cyclisation and Heck reaction

Six-membered ring cyclisation of N-ethylbenzazepinone, prepared from the condensation of benzazepinone with phenethyl iodide under basic conditions, smoothly provided the corresponding product, isoquino[1,2-b][3]benzazepinone, under acid-mediated conditions. On the other hand, the attempted direct five-membered ring cyclisation using the acid-mediated conditions failed to give the 7,5 fused ring isoindolinobenzazepinone from N-benzylbenzazepinone, but the 7,6 fused ring product was instead obtained. However, five-membered ring cyclisation of N-benzylbenzazepinone could be effected efficiently by employing the Heck reaction followed by catalytic hydrogenation to furnish the desired isoindolinobenzazepinone.     

Diels-Alder chemistry of 2-diethoxyphosphinylcyclohex-2-enones. A new approach to complex phosphonates and synthetic applications of the beta-keto phosphonate system

Enone phosphonates 1 and 2 were found to be excellent dienophiles for the Diels-Alder reaction, giving phosphonate-containing polycycles, and the phosphonate group of the resulting adducts facilitated both the installation of an angular alkyl group via a reductive alkylation process and the regioselective generation of a ring junction double bond via an intramolecular Wadsworth-Horner-Emmons reaction.