Ring transformations of heterocyclic compounds. X. A simple method for the conversion of methyl substituted pyridinium salts into 2,4,6-triarylphenyl derivatives: The first (thio)pyrylium ring transformations with heterocyclic anhydrobases as carbon nucleophiles

The synthesis of 2,4,6-triarylphenylpyridinium perchlorates 3 from methyl substituted derivatives 2 by a 2,6-[C₅+C] ring transformation of 2,4,6-triaryl(thio)pyrylium salts 1/4 in the presence of triethylamine/acetic acid in ethanol is reported. Spectroscopic data of the pyridinium perchlorates 3 and their formation via anhydrobases of the salts 2 are discussed.     

Ring transformations of heterocyclic compounds. XIV . Ring transformations of pyrylium and thiopyrylium salts with anhydro-bases derived from 1H-benzimidazolium and benzothiazolium salts: An easy access to 2-(2,4,6-triarylphenyl) 1H-benzimidazolium and benzothiazolium derivatives

The preparation of former unknown 2-(2,4,6-triarylphenyl) substituted 1H-benzimidazolium perchlorates 7 and benzothiazolium perchlorates 8 from 2-methyl substituted derivatives 5/6 by a 2,6-[C₅+C] ring transformation of 2,4,6-triarylpyrylium and 2,4,6-triarylthiopyrylium salts 1/9 in the presence of an appropriate base ( 7 : sodium ethoxide, 8 : sodium acetate) is reported. Spectroscopic data of the transformation products and their mode of formation via anhydrobases of the salts 5/6 are discussed.     

Ring transformations of heterocyclic compounds. XI. 2,4,6-triarylphenylquinolinium salts from methyl substituted derivatives via (thio)pyrylium ring transformations

The preparation of hitherto unknown 2,4,6-triarylphenyl substituted quinolinium perchlorates 3 from methylquinolinium derivatives 2 by a 2,6-[C₅+C] ring transformation of 2,4,6-triaryl(thio)pyrylium salts 1/4 in the presence of triethylamine/acetic acid is described. Spectroscopic data of the quinolinium perchlorates 3 and their formation via anhydrobases of the salts 2 are discussed.     

Ring transformations of heterocyclic compounds. XVI. Spiro[cyclohexadiene-dihydroacridines]. A novel class of spirodihydroacridines by ring transformation of pyrylium salts with 9-methylacridine and its quaternary salts

2,4,6-Triarylpyrylium salts 1 react with the in situ generated anhydrobase of 9,10-dimethylacridinium methosulfate ( 2a ) in the presence of anhydrous sodium acetate in ethanol by a 2,5-[C₄+C₂] pyrylium ring transformation to give the hitherto unknown 6-aroyl-3,5-diaryl-10′-methylspiro[cyclohexa-2,4-diene-1,9′-9′,10′-dihydro-acridines] 3 . When the pyrylium perchlorate 1a is treated under the same conditions with the N-ethyl, N-allyl or N-benzyl substituted acridinium salts 2b-d a dealkylation of these salts occurs and the N-unsubstituted spiro[cyclohexadiene-dihydroacridine] 4a is formed. The same compounds 4 can also be obtained by transformation of the pyrylium salts 1 with 9-methylacridine ( 7 ) and triefhylamine/acetic acid in ethanol. Structure elucidation is performed by an X-ray crystal structure determination of the spiro[cyclohexadiene-dihydroacridine] 3a . Spectroscopic data of the transformation products and their mode of formation are discussed.     

Ring transformations of heterocyclic compounds. XVII, 2-(2,4,6-Triarylphenyl) substituted dihydro-1H-imidazolium,dihydrothiazolium and thiazolium salts from 2-methyl derivatives by pyrylium and thiopyrylium ring transformations

The synthesis of hitherto unknown 2-(2,4,6-triarylphenyl) substituted 4,5-dihydro-1H-imidazolium perchlorates 6 , 4,5-dihydrothiazolium perchlorates 8 and thiazolium perchlorates 9 from their 2-methyl derivatives 2 , 4 and 5 , respectively, by a 2,6-[C₅+C] ring transformation of 2,4,6-triarylpyrylium and -thiopyrylium salts 1/10 in ethanol in the presence of an appropriate base ( 6 : sodium ethanolate; 8,9 : anhydrous sodium acetate) is reported. Spectroscopic data of the transformation products and structural influences on their formation via anhydrobases of the salts 2 , 4 and 5 are discussed.     

Ring transformations of heterocyclic compounds. XV. N-(2-hydroxyphenyl) substituted 2-alkylamino-4,6-diarylbenzophenones by ring transformation of 2,4,6-triarylpyrylium salts with anhydrobases of benzoxazolium salts

The synthesis of hitherto unknown N-(2-hydroxyphenyl) substituted 2-alkylamino-4,6-diarylbenzophenones 3 from 2,4,6-triarylpyrylium salts 1 and 3-alkyl-2-methylbenzoxazolium salts 2 in the presence of triethylamine in ethanol by a 2,5-[C₄+C₂] pyrylium ring transformation is reported. Structure elucidation is performed by an X-ray crystal structure determination of the benzophenone 3a. Spectroscopic data of the transformation products and their mode of formation via anhydrobases of the salts 2 are discussed.     

Reaction of N‐Heterocyclic Silylenes with Thioketone: Formation of Silicon–Sulfur Three (Si‐C‐S)‐ and Five (Si‐C‐C‐C‐S)‐Membered Ring Systems

Three‐ and five‐membered rings that bear the (Si‐C‐S ) and (Si‐C‐C‐C‐S ) unit have been synthesized by the reactions of L SiCl ( 1 ; L =PhC(NtBu)₂) and L′ Si ( 2 ; L′ =CH{(C?CH₂)(CMe)(2,6‐iPr₂C₆H₃N)₂}) with the thioketone 4,4′‐bis(dimethylamino)thiobenzophenone. Treatment of 4,4′‐bis(dimethylamino)thiobenzophenone with L SiCl at room temperature furnished the [1+2]‐cycloaddition product silathiacyclopropane 3 . However, reaction of 4,4′‐bis(dimethylamino)thiobenzophenone with L′ Si at low temperature afforded a [1+4]‐cycloaddition to yield the five‐membered ring product 4 . Compounds 3 and 4 were characterized by NMR spectroscopy, EIMS, and elemental analysis. The molecular structures of 3 and 4 were unambiguously established by single‐crystal X‐ray structural analysis. The room‐temperature reaction of 4,4′‐bis(dimethylamino)thiobenzophenone with L′ Si resulted in products 4 and 5 , in which 4 is the dearomatized product and 5 is formed under the 1,3‐migration of a hydrogen atom from the aromatic phenyl ring to the carbon atom of the C? S unit. Furthermore, the optimized structures of probable products were investigated by using DFT calculations.     

Ring transformations of heterocyclic compounds. XVIII . Spiro[cyclohexadiene-indolines] with three stereocenters from pyrylium salts and chiral methyleneindolines — an example of a high diastereoselective ring transformation

The diastereoselective synthesis of 6-aroyl-3,5-diarylspiro[cyclohexa-2,4-diene-1,2′-indolines] 4 possessing three stereocenters from 2,4,6-triarylpyrylium perchlorates 1 and chiral methyleneindolines 3 (generated in situ by deprotonation of the corresponding 3H-indolium perchlorates 2 ) in the presence of triethylamine/acetic acid in ethanol by a 2,5-[C₄+C₂] pyrylium ring transformation is reported. Structure elucidation is performed by X-ray structure determinations of the spiro[cyclohexadiene-indolines] 4a, 4p and 4t . The influence of various substituents at C-3 of the methyleneindolines 3 on the stereochemistry of the transformation, mechanistic details as well as spectroscopic data of the products 4 are discussed.     

Ring transformations of heterocyclic compounds. XIX. Spiro[dihydropyridine‐indolines] novel heterocycles with two spiro‐condensed N‐containing subunits easy accessible by 1,3‐oxazinium ring transformation

The synthesis of hitherto unknown 1‐benzoyl‐1′,3′,3′‐trimethyl‐4,6‐diphenylspiro[1,2‐dihydropyridine‐2,2′‐indolines] 5 from 2,4,6‐triphenyl‐1,3‐oxazinium tetrafluoroborate ( 1b ) and 1,3,3‐trimethyl‐2‐methyleneindolines 2 (used as such or generated in situ from the corresponding 3H‐indolium salts 4 ) in the presence of triethylamine in anhydrous acetonitrile by a 3,6‐[C₃N+C₂] 1,3‐oxazinium ring transformation is reported. Structure elucidation is performed by an X‐ray structure determination of the spiro[dihydropyridine‐indoline] 5a . Spectroscopic data of the transformation products and their mode of formation are discussed.     

Synthesis and crystal structures of 3D supramolecular compounds: [ M (4,4′-bipy)2(H2O)4] · (4,4′-bipy)2 · (3,5-daba)2 · 8H2O ( M =Zn,Mn)

Two new supramolecular compounds [M(4,4′-bipy)₂ (H₂O)₄] ·?(4,4′-bipy)₂ ·?(3,5-daba)₂ ·?8H₂O (M=Zn(1) or Mn(2), 4,4′-bipy =?4,4′-bipyridine, 3,5-daba =?3,5-diaminobenzoic acid anion) were synthesized and characterized by elemental analysis and X-ray crystal diffraction. In [M(4,4′-bipy)₂(H₂O)₄]²⁺, the M(II) is coordinated by two nitrogen atoms from two 4,4′-bipy molecules and four oxygen atoms from four waters to form an octahedral configuration. There exist uncoordinated 4,4′-bipy molecules, 3,5-diaminobenzolate counterions and water guests in the compounds. The 3D structures of the title supramolecular compounds are constructed by rich hydrogen bonds among [M(4,4′-bipy)₂(H₂O)₄]²⁺, uncoordinated 4,4′-bipy molecules, water molecules and 3,5-daba, containing a diverting hexa-member water ring.     

A novel cadmium(II) coordination polymer with biphenyl‐3,3′,4,4′‐tetra­carboxylic acid and 4,4′‐bipyridine

A novel cadmium(II) coordination polymer, poly[[[bis­(4,4′‐bipyridine)cadmium(II)]‐μ₃‐4,4′‐dicarboxy­biphenyl‐3,3′‐di­carboxyl­ato] 0.35‐hydrate], {[Cd(C₁₆H₈O₈)(C₁₀H₈N₂)₂]·0.35H₂O}_n, was obtained by reaction of Cd(CH₃COO)₂·3H₂O, 4,4′‐bipyridine (4,4′‐bpy) and biphenyl‐3,3′,4,4′‐tetra­car­boxylic acid (H₄L) under hydro­thermal conditions. Each Cd^II atom lies at the centre of a distorted octa­hedron, coordinated by four O atoms from three H₂L²⁻ ligands and N atoms from two monodentate 4,4′‐bpy ligands. Each H₂L²⁻ ligand coordinates to three Cd^II atoms through two carboxyl­ate groups, one acting as a bridging bidentate ligand and the other in a chelating bidentate fashion. Two Cd atoms, two H₂L²⁻ anions and four 4,4′‐bpy ligands form a ring dimer node, which links into an extended broad zonal one‐dimensional chain along the c axis.     

Solvothermal Synthesis and Crystal Structures of Two Manganese Complexes [Mn(II)(acac−)2(4,4′‐bipy)]n (bipy=4,4′‐bipyridine) and [Mn(III)(acac−)3]·4CO(NH2)2

Two special manganese complexes [Mn(II)(acac^?)₂(4,4′‐bipy)]_n (bipy=4,4′‐bipyridine) (complex 1 ) and [Mn(III)(acac^?)₃]·4CO(NH₂)₂ (acacH=acetylacetone) (complex 2 ) were synthesized in the same strategy by solvothermal method. Single crystal X‐ray diffraction revealed the complex 1 consists of one‐dimensional infinite coordination chain, with the manganese centers bridged by 4,4′‐bipy. And free carbamides of complex 2 connect with each other through the hydrogen bonds to form a 14‐membered carbamide ring and a zig‐zag plane. Both enantiomers of Mn(III)(acac^?)₃ exist in the structure, forming a racemate. Furthermore, these enantiomers and those zig‐zag planes are linked with hydrogen bonds to form an unique spatial network.     

Ring transformations of heterocyclic compounds. XX Benzo‐fused spiro[cyclohexadiene‐dihydroindoles] by ring transformation of pyrylium salts with anhydrobases of benzo[e]‐ and benzo[g]indolium salts

The diastereoselective synthesis of 6‐aroyl‐3,5‐diarylspiro[cyclohexa‐2,4‐diene‐1,2′2′,3′‐dihydro‐1′H‐benzo[e]indoles] 6 and ‐benzo[g]indoles] 7 from 2,4,6‐triarylpyrylium perchlorates 1 and in situ generated 2‐methylene‐2,3‐dihydro‐1H‐benzo[e]indoles 3 or ‐benzo[g]indoles 5 (anhydrobases of the corresponding 2‐methyl‐1H‐benzo[e]indolium perchlorates 2 and 2‐methyl‐3H‐benzo[g]indolium perchlorates 4 , respectively) in the presence of triethylamine/acetic acid in ethanol by a 2,5‐[C₄+C₂] pyrylium ring transformation is reported. Spectroscopic data of the transformation products and their mode of formation are discussed.     

Ring transformations of heterocyclic compounds. XXIII. The UV irradiation product of photochromic 2,4,6‐triaryl‐1‐(spiro[2H‐l‐benzopyran‐2,2′‐indoline]‐6‐yl)pyridinium salts ‐ A phenolate betaine or a pyridinium substituted merocyanine dye?

The synthesis of the novel 2,4,6‐triaryl‐1‐(spiro[2H‐1‐benzopyran‐2,2′‐indoline]‐6‐yl)pyridiniumper‐chlorates 4 by reaction of 5 ‐nitrosalicylaldehydes 6 with 1,3,3‐trimethyl‐2‐methyleneindoline ( 7 ) to 6‐nitro‐spiro[2H‐1‐benzopyran‐2,2′‐indolines] 1 , their stannous chloride reduction to the 6‐amino derivatives 8 , followed by a 2,6‐[C₅+N] ring transformation with 2,4,6‐triarylpyrylium perchlorates 9 , is reported. UV irradiation experiments in twenty solvents of different polarity prove their photochromic properties and show that the photochemically generated negative solvatochromic dyes 5 , formed by ring opening of the benzopyran moiety of 4 , are rather merocyanine than pyridinium phenolate betaine dyes.     

Three different fluoro‐ or chloro‐substituted 1′‐deoxy‐1′‐phenyl‐β‐D‐ribofuranoses

Crystal structures are reported for three fluoro‐ or chloro‐substituted 1′‐deoxy‐1′‐phenyl‐β‐D‐ribofuranoses, namely 1′‐deoxy‐1′‐(2,4,5‐trifluorophenyl)‐β‐D‐ribofuranose, C₁₁H₁₁F₃O₄, (I), 1′‐deoxy‐1′‐(2,4,6‐trifluorophenyl)‐β‐D‐ribofuranose, C₁₁H₁₁F₃O₄, (II), and 1′‐(4‐chlorophenyl)‐1′‐deoxy‐β‐D‐ribofuranose, C₁₁H₁₃ClO₄, (III). The five‐membered furanose ring of the three compounds has a conformation between a C2′‐endo,C3′‐exo twist and a C2′‐endo envelope. The ribofuranose groups of (I) and (III) are connected by intermolecular O—H...O hydrogen bonds to six symmetry‐related molecules to form double layers, while the ribofuranose group of (II) is connected by O—H...O hydrogen bonds to four symmetry‐related molecules to form single layers. The O...O contact distance of the O—H...O hydrogen bonds ranges from 2.7172 (15) to 2.8895 (19) Å. Neighbouring double layers of (I) are connected by a very weak intermolecular C—F...π contact. The layers of (II) are connected by one C—H...O and two C—H...F contacts, while the double layers of (III) are connected by a C—H...Cl contact. The conformations of the molecules are compared with those of seven related molecules. The orientation of the benzene ring is coplanar with the H—C1′ bond or bisecting the H—C1′—C2′ angle, or intermediate between these positions. The orientation of the benzene ring is independent of the substitution pattern of the ring and depends mainly on crystal‐packing effects.     

Synthesis of a Thymidine Dimer Containing a Tetrazole‐2,5‐diyl Internucleosidic Linkage and Its Insertion into Oligodeoxynucleotides

Thymidine dimers in which the natural phosphodiester linkage has been replaced by a 2,5‐disubstituted tetrazole ring are synthesized and incorporated into oligodeoxynucleotides (ODNs). The synthesis is accomplished by two strategies based on an alkylation of 5′‐O‐trityl‐on and 5′‐O‐trityl‐off 3′‐deoxy‐3′‐(1H‐tetrazol‐5‐yl)thymidines with 5′‐iodo‐5′‐deoxythymidine in the presence of Et₃N, and the formation of only 2‐substituted tetrazol‐5‐yl linkages is observed in 89 and 46% yields, respectively. The nucleoside dimer formed is reacted with 4,4′‐dimethoxytrityl chloride (DMTCl), followed by treatment with 2‐cyanoethyl tetraisopropylphosphordiamidite in the presence of N,N‐diisopropylammonium tetrazolide, to afford the 5′‐O‐DMT‐protected dinucleoside phosphoramidite that is used for incorporation into ODNs on an automated DNA synthesizer. The modified ODNs with one and up to five tetrazole internucleosidic linkages are obtained in good yields. The thermal stability of DNA/DNA and DNA/RNA duplexes is studied by UV experiments and reported also.     

Coupling and Cyclization of Sydnone Compounds

Cyclization were occurred via the coupling reactions of some mercuric chloride derivatives of sydnone with LiPdCl₃-CuCl₂. A unique six-membered ring, 3,3′-ethylene-4,4′-bissydnone, was obtained by the cyclization reation of 1,2-di[3-(4-chloromercuric)sydnonyl]ethane. However, the seven-membered 3,3′-trimethylene-4,4′-bissydnone and 1,3-di[3-(4-chloro)sydnonyl]-propane were obtained from the corresponding mercuric chlroide of sydnone. Onyl substitution reaction took place when 4,4′-di[3-(4-chloromercuric)sydnonyl]biphenyl, 4,4′-di[3-(4-chloromercuric)sydnonyl]benzene, di(p-[3-(4-chloromercuric)sydnonyl]-phenyl}methane and, di(p-[3-(4-chloromercuric)sydnonyl]phenyl]ether were treated using the same process.     

An experimental study of various arenetricarbonylchromium complexes

For a series of arenetricarbonylchromium complexes ZCr(CO)₃, analysis of the electric dipole moments in benzene and carbonyl stretching frequencies in cyclohexane suggest the following: for unsubstituted ZCr(CO)₃, with Z = diphenyl, fluorene and cis-stilbene, the π-basicity to be considered is that of the ring directly united to the tricarbonylchromium group, and not that of the arene as a whole. In general, the substituent effect in p-substituted diphenyltricarbonylchromium complexes (Z = 4-methyl-, 4-amino- and 4,4′-dimethyldiphenyl), in which the tricarbonylchromium group is bonded to the substituted phenyl ring, is markedly weaker than that in the corresponding benzenetricarbonylchromium complexes. In 4-fluorodiphenyltricarbonylchromium, the tricarbonylchromium group is attached to the unsubstituted phenyl ring. 4-Aminodiphenyltricarbonylchromium exists in two distinct forms: one with the nitrogen lone pair away from, and the other close to, the metal atom. Diphenylmethanetricarbonylchromium (and its 4,4′-diamino derivative), indanetricarbonyl- and 4,4′-difluorodiphenyltricarbonylchromium have also been examined.     

Intramolecular Benzoin Reaction Catalyzed by Benzaldehyde Lyase from Pseudomonas Fluorescens Biovar I

Intramolecular benzoin reactions catalyzed by benzaldehyde lyase from Pseudomonas fluorescens biovar I (BAL) are reported. The structure of the substrates envisaged for this reaction consists of two benzaldehyde derivatives linked by an alkyl chain. The structural requirements needed to achieve the intramolecular carbon–carbon bond reaction catalyzed by BAL were established. Thus, a linker consisting of a linear alkyl chain of three carbon atoms connected through ether‐type bonds to the 2 and 2′ positions of two benzaldehyde moieties, which could be substituted with either Cl, Br, or OCH₃ at either the 3 and 3′ or 5 and 5′ positions, were suitable substrates for BAL. Reactions with 61–84 % yields of the intramolecular product and ee values between 64 and 98 %, were achieved.     

A new three‐dimensional cobalt(II) coordination polymer based on V‐shaped 3,4′‐oxydibenzoate: synthesis,crystal structure and magnetic properties

A new coordination polymer (CP), namely poly[(μ‐4,4′‐bipyridine)(μ₃‐3,4′‐oxydibenzoato)cobalt(II)], [Co(C₁₄H₈O₅)(C₁₀H₈N₂)]_n or [Co(3,4′‐obb)(4,4′‐bipy)]_n ( 1 ), was prepared by the self‐assembly of Co(NO₃)₂·6H₂O with the rarely used 3,4′‐oxydibenzoic acid (3,4′‐obbH₂) ligand and 4,4′‐bipyridine (4,4′‐bipy) under solvothermal conditions, and has been structurally characterized by elemental analysis, IR spectroscopy, single‐crystal X‐ray crystallography and powder X‐ray diffraction (PXRD). Single‐crystal X‐ray diffraction reveals that each Co^II ion is six‐coordinated by four O atoms from three 3,4′‐obb^2? ligands, of which two function as monodentate ligands and the other as a bidentate ligand, and by two N atoms from bridging 4,4′‐bipy ligands, thereby forming a distorted octahedral CoN₂O₄ coordination geometry. Adjacent crystallographically equivalent Co^II ions are bridged by the O atoms of 3,4′‐obb^2? ligands, affording an eight‐membered Co₂O₄C₂ ring which is further extended into a two‐dimensional [Co(3,4′‐obb)]_n sheet along the ab plane via 3,4′‐obb^2? functioning as a bidentate bridging ligand. The planes are interlinked into a three‐dimensional [Co(3,4′‐obb)(4,4′‐bipy)]_n network by 4,4′‐bipy ligands acting as pillars along the c axis. Magnetic investigations on CP 1 disclose an antiferromagnetic coupling within the dimeric Co₂ unit and a metamagnetic behaviour at low temperature resulting from intermolecular π–π interactions between the parallel 4,4′‐bipy ligands.