Enantioselective Access to (−)‐Ambrox® Starting from β‐Farnesene

Starting from inexpensive (E)‐β‐farnesene ( 1 ), an eight‐step enantioselective synthesis of the olfactively precious Ambrox^® ((?)‐ 2a ) has been performed. The crucial step is the catalytic asymmetric isomerization of (2E,6E)‐N,N‐diethylfarnesylamine ( 3 ) to the corresponding enamine (?)‐(R,E)‐ 4a , applying Takasago's well‐known industrial methodology. The resulting dihydrofarnesal ((+)‐(R)‐ 5 ) (90% yield, 96% ee), obtained after in situ hydrolysis (AcOH, H₂O), was then cyclized under catalytic SnCl₄ conditions, via its corresponding unreported enol acetate (?)‐(R)‐ 4b , to afford trans‐decalenic aldehyde (+)‐ 6a . Subsequent transformations furnished bicyclic ketone (?)‐ 8a and unsaturated nitrile (+)‐ 11 , both reported as intermediates to access to (?)‐ 2a .     

Stereo‐Inversion in the (4R)‐γ‐Decanolactone Synthesis by Saccharomyces cerevisiae: (2E,4S)‐4‐Hydroxydec‐2‐enoic Acid Acts as a Key Intermediate

Methyl (2E,4R)‐4‐hydroxydec‐2‐enoate, methyl (2E,4S)‐4‐hydroxydec‐2‐enoate, and ethyl (±)‐(2E)‐4‐hydroxy[4‐²H]dec‐2‐enoate were chemically synthesized and incubated in the yeast Saccharomyces cerevisiae. Initial C‐chain elongation of these substrates to C₁₂ and, to a lesser extent, C₁₄ fatty acids was observed, followed by γ‐decanolactone formation. Metabolic conversion of methyl (2E,4R)‐4‐hydroxydec‐2‐enoate and methyl (2E,4S)‐4‐hydroxydec‐2‐enoate both led to (4R)‐γ‐decanolactone with >99% ee and 80% ee, respectively. Biotransformation of ethyl (±)‐(2E)‐4‐hydroxy(4‐²H)dec‐2‐enoate yielded (4R)‐γ‐[²H]decanolactone with 61% of the ²H label maintained and in 90% ee indicating a stereoinversion pathway. Electron‐impact mass spectrometry analysis (Fig. 4) of 4‐hydroxydecanoic acid indicated a partial C(4)→C(2) ²H shift. The formation of erythro‐3,4‐dihydroxydecanoic acid and erythro‐3‐hydroxy‐γ‐decanolactone from methyl (2E,4S)‐4‐hydroxydec‐2‐enoate supports a net inversion to (4R)‐γ‐decanolactone via 4‐oxodecanoic acid. As postulated in a previous work, (2E,4S)‐4‐hydroxydec‐2‐enoic acid was shown to be a key intermediate during (4R)‐γ‐decanolactone formation via degradation of (3S,4S)‐dihydroxy fatty acids and precursors by Saccharomyces cerevisiae.     

Hydrogen‐bonded networks in 5‐chloropyridin‐2‐amine–fumaric acid (2/1) and 2‐aminopyridinium dl‐malate

Crystals of 5‐chloropyridin‐2‐amine–(2E)‐but‐2‐enedioate (2/1), 2C₅H₅ClN₂·C₄H₄O₄, (I), and 2‐aminopyridinium dl ‐3‐carboxy‐2‐hydroxypropanoate, C₅H₇N₂⁺·C₄H₅O₅⁻, (II), are built from the neutral 5‐chloropyridin‐2‐amine molecule and fumaric acid in the case of (I) and from ring‐N‐protonated 2‐aminopyridinium cations and malate anions in (II). The fumaric acid molecule lies on an inversion centre. In (I), the neutral 5‐chloropyridin‐2‐amine and fumaric acid molecules interact via hydrogen bonds, forming two‐dimensional layers parallel to the (100) plane, whereas in (II), oppositely charged units interact via ionic and hydrogen bonds, forming a three‐dimensional network.     

Synthesis of Racemic Δ3‐2‐Hydroxybakuchiol and Its Analogues

The first synthetic approach to (±)‐Δ³‐2‐hydroxybakuchiol (=4‐[(1E,5E)‐3‐ethenyl‐7‐hydroxy‐3,7‐dimethylocta‐1,5‐dien‐1‐yl]phenol; 14 ) and its analogues 13a – 13f was developed by 12 steps (Schemes 2 and 3). The key features of the approach are the construction of the quaternary C‐center bearing the ethenyl group by a Johnson–Claisen rearrangement (→ 6 ); and of an (E)‐alkenyl iodide via a Takai–Utimoto reaction (→ 11 ); and an arylation via a Negishi cross‐coupling reaction (→ 12e – 12f ).     

Synthesis and Structure of Lanthanide Sandwich Complexes with Mixed Cyclooctatetraenyl and Chelating Substituted‐indenyl Ligands

Two types of sandwich complexes (η⁵‐MeOCH₂CH₂C₉H₆) Ln (η⁸‐C₈H₈) (THF)_n [Ln=La (1), Nd(2), n=0; Sm(3), Dy (4) and Er (5). n = l] and (η⁵‐C₄H₇OCH₂C₉H₆)Ln(η⁸‐C₈H₈) (THF) [Ln = La (6), Nd(7). Sm(8). Dy (9) and Er (10)] were synthesized by the reactions of LnCl₃ with equivalent mole of K₂C₈H₈, followed by treatment with corresponding potassium salt of ether‐substituted indenide. The molecular structures of 3 and 8 were determined by single crystal X‐ray diffraction. (η⁵ ‐MeOCH₂CH₂C₉H₆) Sm (η⁸‐C₈H₈) (THF) (3) monoclinic. Pt₁/c, a = 1.4793(3) nm, b = 0.8716 (2) nm, c = 1.6149 (3) nm, β = 98. 17(3), V = 2.0612(7) nm³, Z = 4, R(F)=0.0362. (η⁵‐C₄H₇OCH₂C₉H₆)Sm(η⁸‐C₈H₈)(THF) (8) orthorhombic. p2₁2₁2₁. a = 0.8754(2) nm, b = 1.1000(2) nm, c = 2.3117 (5) nm, V = 2.2260(8) nm³, Z=4, R(F) =0.0497.     

Lewis Acid Catalyzed,Selective Cyclopropane‐Ring Opening in Ingol Diterpene Derivatives

Lewis acid mediated skeletal rearrangement of the ingol diterpenoids 1 and 4 via regio‐ and stereospecific cyclopropane‐ring opening afforded the four new compounds 2, 3, 5 , and 6 , named nivulianol A–D (Scheme 1). Their structures were established by means of IR, MS, and in‐depth NMR spectroscopic analyses. The rearranged congeners were tested for lipopolysaccharide (LPS)‐induced prostaglandin (PG) E₂ (cyclooxygenase‐2) inhibition. Thereby, nivulianol B (=(1S*,2E,4R*,5S*,7Z,9S*,11R,13S*,14S*)‐14‐acetoxy‐5‐methoxy‐3,9,13‐trimethyl‐6‐(1‐methylethenyl)‐10‐oxo‐15‐oxatricyclo[9.3.1.0^1,11]pentadeca‐2,7‐dien‐4‐yl (2Z)‐2‐methylbut‐2‐enoate; 3 ) was found to be significantly active, with an IC₅₀ value of 36.3 μg/ml.     

Synthesis of double silylene‐bridged binuclear zirconium complexes and their use as catalysts for olefin polymerization

New double silylene‐bridged binuclear zirconium complexes [(η⁵‐RC₅H₄)ZrCl₂]₂[μ,μ‐(SiMe₂)₂(η⁵‐C₅H₃)₂] [R = H ( 1 ), Me ( 2 ), ⁿPr ( 3 ), ⁱPr ( 4 ), ⁿBu ( 5 ), allyl ( 6 ), 3‐butenyl ( 7 ), benzyl ( 8 ), PhCH₂CH₂ ( 9 ), MeOCH₂CH₂ ( 10 )] were synthesized by the reaction of (η⁵‐RC₅H₄)ZrCl₃·DME with [μ,μ‐(SiMe₂)₂(η⁵‐C₅H₃)₂]^2? ( L^2? ) in THF, and they were all well characterized by ¹H NMR, MS, IR, and EA. The binuclear structure of Complex 3 was further confirmed by X‐ray diffraction, where the two zirconium centers are located trans relative to the bridging [μ,μ‐(SiMe₂)₂(η⁵‐C₅H₃)₂] moiety. When activated with methylaluminoxane (MAO), this series of zirconium complexes are highly active catalysts for the polymerization of ethylene even under very low molar ratio of Al/Zr (Complex 7 , 5.41 × 10⁵ g‐PE/mol‐Zr·h, Al/Zr = 50) and linear polyethylenes (PEs) with broad molecular weight distribution (MWD, M_w/M_n = 7.31–27.6) was obtained. The copolymerization experiments indicate that these complexes are also very efficient in the incorporation of 1‐hexene into the growing PE chain in the presence of MAO (Complex 6 , 3.59 × 10⁶ g‐PE/mol‐Zr·h; 1‐hexene content, 3.65%). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4901–4913, 2007     

Efficient Synthesis of a Styryl Analogue of (2S,3R,4E)‐N2‐Octadecanoyl‐4‐tetradecasphingenine via Cross‐Metathesis Reaction

The first total synthesis of sphingolipid (2S,3R,4E)‐N²‐octadecanoyl‐4‐tetradecasphingenine ( 1a ), a natural sphingolipid isolated from Bombycis Corpus 101A, and of its styryl analogue 1b was achieved in good overall yield (Schemes 1 and 2). The key step involved the installation with (E) stereoselectivity of a long lipophilic chain or phenyl group on allyl alcohol derivative 3 via a cross‐metathesis reaction (→ 5a or 5b ). The N‐Boc protected 3 was easily accessible from (S)‐Garner aldehyde.     

Metabolism of Deuterated erythro‐Dihydroxy Fatty Acids in Saccharomyces cerevisiae: Enantioselective Formation and Characterization of Hydroxylactones

Epoxides of fatty acids are hydrolyzed by epoxide hydrolases (EHs) into dihydroxy fatty acids which are of particular interest in the mammalian leukotriene pathway. In the present report, the analysis of the configuration of dihydroxy fatty acids via their respective hydroxylactones is described. In addition, the biotransformation of (±)‐erythro‐7,8‐ and ‐3,4‐dihydroxy fatty acids in the yeast Saccharomyces cerevisiae was characterized by GC/EI‐MS analysis. Biotransformation of chemically synthesized (±)‐erythro‐7,8‐dihydroxy(7,8‐²H₂)tetradecanoic acid ((±)‐erythro‐ 1 ) in the yeast S. cerevisiae resulted in the formation of 5,6‐dihydroxy(5,6‐²H₂)dodecanoic acid ( 6 ), which was lactonized into (5S,6R)‐6‐hydroxy(5,6‐²H₂)dodecano‐5‐lactone ((5S,6R)‐ 4 ) with 86% ee and into erythro‐5‐hydroxy(5,6‐²H₂)dodecano‐6‐lactone (erythro‐ 8 ). Additionally, the α‐ketols 7‐hydroxy‐8‐oxo(7‐²H₁)tetradecanoic acid ( 9a ) and 8‐hydroxy‐7‐oxo(8‐²H₁)tetradecanoic acid ( 9b ) were detected as intermediates. Further metabolism of 6 led to 3,4‐dihydroxy(3,4‐²H₂)decanoic acid ( 2 ) which was lactonized into 3‐hydroxy(3,4‐²H₂)decano‐4‐lactone ( 5 ) with (3R,4S)‐ 5 =88% ee. Chemical synthesis and incubation of (±)‐erythro‐3,4‐dihydroxy(3,4‐²H₂)decanoic acid ((±)‐erythro‐ 2 ) in yeast led to (3S,4R)‐ 5 with 10% ee. No decano‐4‐lactone was formed from the precursors 1 or 2 by yeast. The enantiomers (3S,4R)‐ and (3R,4S)‐3,4‐dihydroxy(3‐²H₁)nonanoic acid ((3S,4R)‐ and (3R,4S)‐ 3 ) were chemically synthesized and comparably degraded by yeast without formation of nonano‐4‐lactone. The major products of the transformation of (3S,4R)‐ and (3R,4S)‐ 3 were (3S,4R)‐ and (3R,4S)‐3‐hydroxy(3‐²H₁)nonano‐4‐lactones ((3S,4R)‐ and (3R,4S)‐ 7 ), respectively. The enantiomers of the hydroxylactones 4, 5 , and 7 were chemically synthesized and their GC‐elution sequence on Lipodex^® E chiral phase was determined.     

Electrospray ionization mass spectrometry of tributyltin(IV) complexes and their larvicidal activity on mosquito larvae: crystal and molecular structure of polymeric (Bu3Sn[O2CC6H4{NN(C6H3‐4‐OH(C(H)NC6H4OCH3‐4))}‐o])n

A series of tributyltin(IV) complexes of 2‐[(E)‐2‐(3‐formyl‐4‐hydroxyphenyl)‐1‐diazenyl]benzoic acid and 4‐[((E)‐1‐{2‐hydroxy‐5‐[(E)‐2‐(2‐carboxyphenyl)‐1‐diazenyl]phenyl}methylidene)amino]aryls have been investigated by electrospray mass spectrometry (ESI‐MS) and tandem mass spectrometry (MSⁿ) techniques. The assignments are facilitated by agreement between observed and calculated isotopic patterns and MSⁿ studies. Single‐crystal X‐ray crystallography of (Bu₃Sn[O₂CC₆H₄{N?N(C₆H₃‐4‐OH(C(H)?NC₆H₄OCH₃‐4))}‐o])_n reveals a polymeric structure. Toxicity studies of the tributyltin(IV) complexes of the 4‐[((E)‐1‐{2‐hydroxy‐5‐[(E)‐2‐(2‐carboxyphenyl)‐1‐diazenyl]phenyl}methylidene)amino]aryls on the second larval instar of the Aedes aegypti and Anopheles stephensi mosquito larvae are also reported. The LC₅₀ values indicate that the complexes are effective larvicides, which range from a low of 0.36 ppm to a high of 0.69 ppm against the Ae. aegypti larvae and between 0.82 and 1.17 ppm against the An. stephensi larvae. Copyright © 2005 John Wiley & Sons, Ltd.     

The first square‐planar copper(II) 1:2 complex with differently coordinated 2‐hydroxybenzaldehyde 4‐allylthiosemicarbazone ligands

The title compound, [(Z)‐4‐allyl‐2‐(2‐hydroxybenzylidene)thiosemicarbazide‐κS][(E)‐4‐allyl‐1‐(2‐oxidobenzylidene)thiosemicarbazidato‐κ³O,N¹,S]copper(II) monohydrate, [Cu(C₁₁H₁₁N₃OS)(C₁₁H₁₃N₃OS)]·H₂O, crystallized as a rotational twin in the monoclinic crystal system (space group Cc) with two formula unit (Z′ = 2) in the asymmetric unit, one of which contains an allyl substituent disordered over two positions. The Cu^II atom exhibits a distorted square‐planar geometry involving two differently coordinated thiosemicarbazone ligands. One ligand is bonded to the Cu^II atom in a tridentate manner via the phenolate O, azomethine N and thioamide S atoms, while the other coordinates in a monodentate manner via the S atom only. The complex is stabilized by an intramolecular hydrogen bond, which creates a six‐membered pseudo‐chelate metalla‐ring. The structure analysis indicates the presence of the E isomer for the tridentate ligand and the Z isomer for the monodentate ligand. The crystal structure contains a three‐dimensional network built from intermolecular O—H...O, N—H...O, O—H...N and N—H...S hydrogen bonds.     

Caulerpenyne-Amine Reacting System as a Model for in vivo Interactions of Ecotoxicologically Relevant Sesquiterpenoids of the mediterranean-adapted tropical green seaweed caulerpa taxifolia

Caulerpenyne ( 1 ), the most abundant of the ecotoxicologically relevant sesquiterpenoids of the Mediterranean-adapted tropical green seaweed Caulerpa taxifolia, was found to react with Et₃N or pyridine in MeOH by initial deprotection of C(1)HO to give oxytoxin 1 ( 2a ), previously isolated from the sacoglossan mollusc Oxynoe olivacea. With BuNH₂, without any precaution to exclude light, 1 gave the series of racemic 3 and 4 , and achiral (4E,6E)- 5 , (4E,6Z)- 5 , (4Z,6E)- 5 , and (4Z,6Z)- 5 pyrrole compounds, corresponding to formal C(4) substitution, 4,5-β-elimination, and (E/Z)-isomerization at the C(4)?C(5) and C(6)?C(7) bonds. Changing to CDCl₃ as solvent in the dark, 1 gave cleanly, via 2a as an intermediate, 3 and (4E,6E)- 5 . The latter proved to be prone to (E/Z)-photoisomerization. Under standard acetylation conditions, 3 gave (4E,6E)- 5 via acetamide 7 as an intermediate. Particular notice is warranted by selective deprotection of 1 at C(1), mimicking enzyme reactions, and unprecedented formation of pyrrole compounds from freely-rotating, protected 1,4-dialdehyde systems.     

X‐ray structures,spectroscopic, electrochemical,thermal, antibacterial,and DFT studies of two nickel(II) and cobalt(III) complexes constructed from a new quinazoline‐type ligand

Two two‐dimensional supramolecular Nickel(II) and Cobalt(III) complexes, [Ni( L ² )₂]·2CH₃OH ( 1 ) and [2Co( L ² )₂] ( 2 ) ( HL ²  = 1‐(2‐{[(E)‐3‐bromo‐5‐chloro‐2‐hydroxybenzylidene]amino}phenyl)ethanone oxime), were synthesized via complexation of salts acetate with HL ¹ (2‐(3‐bromo‐5‐chloro‐2‐hydroxyphenyl)‐4‐methyl‐1,2‐dihydroquinazoline 3‐oxide, H is the deprotonatable hydrogen). During the reaction, the C–N bond in HL ¹ is converted into the C=N–OH group in HL ² . The spectroscopic data of both complexes were compared with the ligand HL ¹ . HL ¹ and both complexes were determined by single‐crystal X‐ray crystallography. The differently geometric features of the obtained complexes 1 and 2 are observed. In the crystal structure, 1 and 2 form an infinite 1‐D chain‐like and 2‐D supramolecular frameworks. EPR spectroscopy of 2 was investigated. Moreover, electrochemical properties and antimicrobial activities of both complexes were also studied. In addition, the calculated HOMO and LUMO energies show the character of HL ¹ , complexes 1 and 2 . The electronic transitions and spectral features of HL ¹ and both complexes were discussed by TD‐DFT calculations.     

Solvatomorphism in (E)‐2‐(2,6‐dichloro‐4‐hydroxybenzylidene)hydrazinecarboximidamide

The structures of orthorhombic (E)‐4‐(2‐{[amino(iminio)methyl]amino}vinyl)‐3,5‐dichlorophenolate dihydrate, C₈H₈Cl₂N₄O·2H₂O, (I), triclinic (E)‐4‐(2‐{[amino(iminio)methyl]amino}vinyl)‐3,5‐dichlorophenolate methanol disolvate, C₈H₈Cl₂N₄O·2CH₄O, (II), and orthorhombic (E)‐amino[(2,6‐dichloro‐4‐hydroxystyryl)amino]methaniminium acetate, C₈H₉Cl₂N₄O⁺·C₂H₃O₂⁻, (III), all crystallize with one formula unit in the asymmetric unit, with the molecule in an E configuration and the phenol H atom transferred to the guanidine N atom. Although the molecules of the title compounds form extended chains via hydrogen bonding in all three forms, owing to the presence of different solvent molecules, those chains are connected differently in the individual forms. In (II), the molecules are all coplanar, while in (I) and (III), adjacent molecules are tilted relative to one another to varying degrees. Also, because of the variation in hydrogen‐bond‐formation ability of the solvents, the hydrogen‐bonding arrangements vary in the three forms.     

A square‐planar tellurium(II) complex with Te,Te′‐chelating ligands

While exploring the chemistry of tellurium‐containing dichalcogenidoimidodiphosphinate ligands, the first all‐tellurium member of a series of related square‐planar E^II(E′)₄ complexes (E and E′ are group 16 elements), namely bis(P,P,P′,P′‐tetraphenylditelluridoimidodiphosphinato‐κ²Te,Te′)tellurium(II) (systematic name: 2,2,4,4,8,8,10,10‐octaphenyl‐1λ³,5,6λ⁴,7λ³,11‐pentatellura‐3,9‐diaza‐2λ⁵,4λ⁵,8λ⁵,10λ⁵‐tetraphosphaspiro[5.5]undeca‐1,3,7,9‐tetraene), C₄₈H₄₀N₂P₄Te₅, was obtained unexpectedly. The formally Te^II centre is situated on a crystallographic inversion centre and is Te,Te′‐chelated to two anionic [(TePPh₂)₂N]⁻ ligands in an anti conformation. The central Te^II(Te)₄ unit is approximately square planar [Te—Te—Te = 93.51 (3) and 86.49 (3)°], with Te—Te bond lengths of 2.9806 (6) and 2.9978 (9) Å.     

(1E,3E,5E)‐1,2,3,4,5,6‐Hexa­fluoro‐1,6‐di­phenyl­hexatriene

The title triene, C₁₈H₁₀F₆, was prepared via the Pd⁰ coupling reaction of (E)‐(1,2‐di­fluoro‐1,2‐ethenediyl)­bis­(tri­butyl­stan­nane) with (Z)‐β‐iodo‐α,β‐di­fluoro­styrene in N,N′‐dimethylformamide/tetrahydrofuran. The crystal structure shows the product to be the 1E,3E,5E isomer. Due to steric interactions between F atoms, the double bonds are not coplanar. The planes defined by the two terminal double bonds are almost perpendicular.     

Synthesis and characterization of bromo‐, arylazo‐, and heterocyclic‐fused troponoids containing a 1,3‐benzodioxole system

A facile synthesis of a series of novel bromo‐, arylazo‐, and heterocyclic fused troponoid compounds containing 1,3‐benzodioxole system is described. The 7‐bromo‐, 5,7‐dibromo‐, and 5‐arylazo‐substituted 3‐[(2E)‐3‐(1,3‐benzodioxol‐5‐yl)prop‐2‐enoyl]tropolones ( 2 , 3 , and 5 , 6 , 7 ) were obtained by direct bromination or azo‐coupling reactions of 3‐[(2E)‐3‐(1,3‐benzodioxol‐5‐yl)prop‐ 2‐enoyl]tropolone ( 1 ) with bromine, and diazonium salts of aniline derivatives, respectively. 3‐[(2E)‐3‐(1,3‐Benzodioxol‐5‐yl)prop‐2‐enoyl]‐5‐bromotropolone ( 4 ) was obtained from 3‐acetyl‐5‐bromotropolone via one‐pot aldol dehydration reaction with piperonal. Tropolones 2, 3 , and 4 were subjected to nucleophilic cyclization with bifunctional hydroxylamine hydrochloride and phenylhydrazine hydrochloride to give the corresponding isoxazolo‐ and pyrazolo‐fused tropones ( 8 , 9 , 10 , 11 , 12 , 13 ), respectively. J. Heterocyclic Chem., (2012).     

The Role of Ion Pairs in the Second‐Order NLO Response of 4‐X‐1‐Methylpiridinium Salts

A series of 4‐X‐1‐methylpyridinium cationic nonlinear optical (NLO) chromophores (X=(E)‐CH?CHC₆H₅; (E)‐CH?CHC₆H₄‐4′‐C(CH₃)₃; (E)‐CH?CHC₆H₄‐4′‐N(CH₃)₂; (E)‐CH?CHC₆H₄‐4′‐N(C₄H₉)₂; (E,E)‐(CH?CH)₂C₆H₄‐4′‐N(CH₃)₂) with various organic (CF₃SO₃^?, p‐CH₃C₆H₄SO₃^?), inorganic (I^?, ClO₄^?, SCN^?, [Hg₂I₆]^2?) and organometallic (cis‐[Ir(CO)₂I₂]^?) counter anions are studied with the aim of investigating the role of ion pairing and of ionic dissociation or aggregation of ion pairs in controlling their second‐order NLO response in anhydrous chloroform solution. The combined use of electronic absorption spectra, conductimetric measurements and pulsed field gradient spin echo (PGSE) NMR experiments show that the second‐order NLO response, investigated by the electric‐field‐induced second harmonic generation (EFISH) technique, of the salts of the cationic NLO chromophores strongly depends upon the nature of the counter anion and concentration. The ion pairs are the major species at concentration around 10^?3 M , and their dipole moments were determined. Generally, below 5×10^?4 M , ion pairs start to dissociate into ions with parallel increase of the second‐order NLO response, due to the increased concentration of purely cationic NLO chromophores with improved NLO response. At concentration higher than 10^?3 M , some multipolar aggregates, probably of H type, are formed, with parallel slight decrease of the second‐order NLO response. Ion pairing is dependent upon the nature of the counter anion and on the electronic structure of the cationic NLO chromophore. It is very strong for the thiocyanate anion in particular and, albeit to a lesser extent, for the sulfonated anions. The latter show increased tendency to self‐aggregate.     

Two‐ and Three‐Component Reactions Leading to New Enamines Derived from 2,3‐Dicyanobut‐2‐enoates

The three‐component reactions of 1‐azabicyclo[1.1.0]butanes 1 , dicyanofumarates (E)‐ 5 , and MeOH or morpholine yielded azetidine enamines 8 and 9 with the cis‐orientation of the ester groups at the C?C bond ((E)‐configuration; Schemes 3 and 4). The structures of 8a and 9d were confirmed by X‐ray crystallography. The formation of the products is explained via the nucleophilic addition of 1 onto (E)‐ 5 , leading to a zwitterion of type 7 (Scheme 2), which is subsequently trapped by MeOH or morpholine ( 10a ), followed by elimination of HCN. Similarly, two‐component reactions between secondary amines 10a – 10c and (E)‐ 5 gave products 12 with an (E)‐enamine structure and (Z)‐oriented ester groups. On the other hand, two‐component reactions involving primary amines 10d – 10f or NH₃ led to the formation of the corresponding (Z)‐enamines, in which the (E)‐orientation of ester groups was established.     

A synthetic zinc tellurium oxochloride,Zn2(TeO3)Cl2

Single crystals of dizinc tellurium dichloride trioxide, Zn₂(TeO₃)Cl₂, were synthesized via a transport reaction in sealed evacuated glass tubes. The compound has a layered structure in which the building units are [ZnO₄Cl] square pyramids, distorted [ZnO₂Cl₂] tetrahedra and [TeO₃E] tetrahedra (E is the 5s² lone pair of the Te^IV atom), joined through shared edges and corners to form charge‐neutral layers. Cl atoms and Te‐atom lone pairs protrude from the surfaces of each layer towards adjacent layers, and the layers are held together by dispersion forces only. The compound is isostructural with the synthetic compound CuZn(TeO₃)Cl₂ and the mineral sophiite, Zn₂(SeO₃)Cl₂.