Selective synthesis of isomeric heterodinuclear complexes with switched metal arrangements via proton-induced reversible metal migration

Pairs of isomeric heterodinuclear complexes, [(cod)Ir(mu-PNNN)M(L)]BF4 and [(L)M(mu-PNNN)Ir(cod)]BF4, with switched metal arrangements are prepared in a specific manner by simply changing the addition order of the reagents.     

The synthesis of four isomeric bisthienothiepinones

The displacement reaction between sodium thiophene-3-thiolate and methyl 3-(bromomethyl)thiophene-2-carboxylate ( 5 ) gave the expected thioether 7a . Basic hydrolysis afforded the carboxylic acid 7b ; conversion to the acid chloride, and treatment of the latter with stannic chloride then produced the bisthienothiepinone 1 . Using analogous reactions the isomers 2-4 were also synthesized.     

One-pot synthesis of isomeric 2-hydroxyphenyl-substituted cycloalkatetrazolopyrimidines

Russian Journal of Organic Chemistry - Three-component condensation of salicylaldehyde with tetrazol-5-amine and cycloheptanone (cyclooctanone) gave isomeric 2-hydroxyphenyl-substituted...     

One-step synthesis of novel tricyclic isomeric azidonucleosides

Several tricyclic azido-isonucleosides were formed in high yields by the treatment of pyrimidine isonucleosides with triphenylphosphine, tetrabromomethane, and sodium azide. The regioselective ring opening of these tricyclic azido-isonucleosides was also investigated.     

Fischer synthesis of isomeric thienopyrrole LHRH antagonists

As part of a structure–activity exploration into LHRH antagonists, structures containing the thieno[2,3-b]pyrrole core were identified as potent antagonists. This letter describes the employment of the Fischer synthesis to access this thienopyrrole and isomeric final compounds.     

Facile synthesis and coupling of functionalized isomeric biquinolines

A simple route toward functionalized biquinolines, namely 8,5′-dibromo-5,8′-biquinoline 1 and 5,5′-dibromo-8,8′-biquinoline 2, was developed using Skraup syntheses. Both the dibromo compounds undergo facile Suzuki coupling to afford fluorene-coupled products 3 and 4, respectively, an important transformation in designing conjugated materials based on these cores. X-ray structural analyses of 1 and 4 provide insight into the mode of packing within materials containing these units.     

Convergent synthesis of isomeric pairs of metallocene-containing polyether macrocycles

A general method for rapid construction of metallocene-based hosts is described. Treatment of polyether bridged bis(diphenylacetylenes) with a source of cyclopentadienyl cobalt at high temperature leads, via macrocyclization and capture of the intermediate cyclobutadiene, to macrocyclic systems tethered to an integral metallocene platform. Equal yields of the two possible structural isomers, the products of parallel or antiparallel cycloaddition of the precursor, are obtained. A combination of X-ray crystallography and NMR is employed to assign structures to the individual isomers and to assess the strength of lithium ion binding by the individual macrocycles.     

Asymmetric synthesis and cytotoxic activity of isomeric phytosphingosine derivatives

New phytosphingosine analogues have been conceived, synthesised and their cytotoxicity in B16 murine melanoma cells tested. These compounds embed an isomeric substitution pattern resulting from a formal permutation of the C-2 and C-4 substituents along the aliphatic skeleton of the original sphingoid base. Five different stereoisomers have been accessed through regio- and stereocontrolled opening of the oxirane of long chain epoxyamine precursors. The corresponding N-hexyl and N-octanoyl derivatives have also been prepared. In cell viability experiments all the primary amines were found to be more active than the natural phytosphingosine with IC(50) in the low μM range for the most potent compounds.     

The synthesis of bisitaconamic acids and isomeric bisimide monomers

Members of a series of N,N′-alkylene bisitaconamic acids were synthesized from the reaction between itaconic anhydride and a homologous group of aliphatic diamines with the general formula H₂N (CH₂)_n NH₂, where n = 4–12. Cyclodehydration of the acids in toluene gave the isomeric imides: bisitaconimide, biscitraconimide, and citra-itaconimide. The isomeric imides were isolated, purified, and characterized for each diaminoalkane studied.     

Studies in the synthesis and interconversion of isomeric triazolothienopyrimidines

4-Hydrazinothieno[2,3-d]pyrimidines were cyclized with triethyl orthoformate and formic acid to give 1,2,4-triazolo[4,3-c]thieno[3,2-e]pyrimidines and 1,2,4-triazolo[2,3-c]thieno[3,2-e]pyrimidines depending on the reaction conditions employed.     

Selective synthesis of meso-naphthylporphyrins

A series of novel meso-(8-substituted naphth-1-yl)porphyrins has been synthesized creating derivatives with a tight recognition environment above the porphyrin plane. The selective synthesis of single atropisomers is discussed. Condensation of bisnaphthaldehyde 12 with phenyldipyrromethane unexpectedly led to selective synthesis of the alpha,alpha-5,10-bridged isomer 14. A mechanism is proposed for this unusual scrambling, and alternative syntheses of alpha,alpha-5,15-bisnaphthylporphyrins are described. Synthesis of 5,15-analogues can be achieved by employing (pentafluorophenyl)dipyrromethane or via presynthesis of a bis(dipyrromethane) derivative 22 (from bisnaphthaldehyde 12) and subsequent condensation with benzaldehyde.     

Selective synthesis, structure and oxidation properties of isomeric 1,4-dithiins fused to two benzo[b]thiophenes

Two novel isomers of 1,4-dithiins fused to two benzo[b]thiophenes on both sides were obtained by selective synthetic methods via the corresponding sulfides. The crystal structures of two dithiins were determined by X-ray crystallographic analyses. Examination of oxidation properties of the dithiins showed interesting results by CV measurement. The ESR spectra of chemically oxidized dithiins indicated formation of stable radical cations.     

Studies of synthesis and cationic photopolymerization of three isomeric monoterpene diepoxides

The monoterpene diepoxides isoascaridole ( III ), γ-terpinene diepoxide ( V ), and limonene diepoxide ( VIII ) were prepared from the corresponding hydrocarbons and their reactivity in photoinitiated cationic polymerization examined. Both V and VIII underwent facile and rapid polymerization to give crosslinked polyethers III , but although highly reactive, did not undergo crosslinking polymerization. With the aid of model compounds it was determined that the rearrangement of one of the epoxy groups of III takes place in the presence of photogenerated acid to give an epoxy ketone ( XIII ) as the primary product. XIII undergoes very sluggish polymerization. © 1995 John Wiley & Sons, Inc.     

The synthesis of isomeric 4- and 6-ethoxy-3-ethylpyridines

The synthesis of isomeric 4- and 6-ethoxy-3-ethylpyridines has been effected and a difference in the behavior of substituents in the - and -positions of the isomeric pyridine derivatives has been observed.     

Selective synthesis of some imidazopyridine-fused chromones

A fused heterocyclic scaffold combining the imidazo[1,2-a]pyridine with a substituted chromone was synthesized in a one-pot procedure. The reaction proceeds by intramolecular cyclization of 1-(2-imino-2H-chromen-3-yl)pyridinium chloride in ethanol and in the presence of DABCO. A detailed study of the experimental conditions allowed a clear understanding of the reaction pathway.     

Selective synthesis of monoaryl substituted porphyrins

A synthetic route to meso-monoarylporphyrins using a MacDonald-type 2 + 2 condensation is described. In this method a bisformyl substituted dipyrrylmethane is treated with a biscarboxydipyrrylmethane. The 5-aryldipyrrylmethanes 15, 25 and 27 were obtained by condensation of the corresponding pyrroles 18, 28 and 29 respectively with benzaldehyde in presence of p-toluenesulfonic acid.