Selective reduction of tertiary alkyl,benzyl, and allyl halides to hydrocarbons using lithium 9,9-di-n-butyl-9-borabicyclo[3.3.1]nonanate

The title 9-borabicyclo[3.3.1]nonane(9-BBN) ate complex (1) brings about selective removal of tertiary alkyl, benzyl and allyl halides to give the corresponding hydrocarbons in excellent yields without concomitant attack on secondary, primary and aryl derivatives. The reduction of cis- and trans - 4 - t - butyl - 1 - methylcyclohexyl chlorides (2) with 1 gives 4 - t - butyl - 1 - methylcyclohexanes (3) with partial inversion of configuration in cyclohexane, while that in benzene gives thermodynamically stable trans-3 predominantly. The reactions of 1,1 - dimethyl - 5 - hexenyl chloride (4) and 1,7,7 - trimethylbicyclo[2.2.1]hept - 2 - yl chloride (8) with 1 proceed with the rearrangements characteristic to a carbonium ion intermediate. The reduction of 1 - ethyl - 1 - methylpentyl chloride with 1 follows a second-order rate equation.     

Transition metal complexes with pyrazole-based ligands. Part 28. Synthesis,structural, DFT and thermal studies of cadmium(II) halides and zinc(II) chloride complexes with 3,5-dimethylpyrazole-1-carboxamidine

The complex formation of 3,5-dimethylpyrazole-1-carboxamidinium nitrate, HL·HNO₃ with ammine complexes of cadmium(II) halides (Cl, Br, I) and zinc(II) chloride has been investigated under self-controlled reaction conditions. The complexes have been characterized by X-ray diffraction, FT-IR spectroscopy, thermal analysis and quantum chemical calculations. In the case of cadmium bromide and iodide salts, isostructural complexes with composition of [CdX₂(HL)₂] were formed. With CdCl₂ a binuclear octahedral [Cd₂(HL)₄(μ-Cl)₂](NO₃)₂ complex is obtained. Zinc(II) chloride with HL·HNO₃ gives [Zn(HL)₂Cl]NO₃, the zinc center exhibiting severely distorted five-coordinate stereochemistry, intermediate between an ideal trigonal bipyramid and a square pyramid. The course of complex formation as well as the thermal properties of the compounds has been explained using the HSAB principle. The assignment of the FT-IR spectra was supported by DFT computations.     

Application of the Blaise reaction: stereoselective synthesis of (4R)-tert-butyl 3-amino-4-trimethylsilyloxy-2-alkenoates from (R)-cyanohydrins

O-Trimethylsilyl protected (R)-cyanohydrins 3 react with Reformatsky reagents from tert-butyl 2-bromoesters 4 and zinc dust (Blaise reaction) to give the corresponding addition products in high yields. Workup with an aqueous solution of NH₄Cl at low temperature gives (4R)-tert-butyl 3-amino-4-trimethylsilyloxy-2-alkenoates (R)-5 without racemization. Hydrogenation of the alkenoates 5 to the corresponding tert-butyl β-amino-γ-hydroxyalkanoates 6, resulting in a mixture of two diastereoisomers, was only possible under special hydrogenation conditions. With HCl in dichloromethane compounds 6 cyclize to the corresponding β-amino-γ-hydroxybutyrolactones 8.     

Zur Kenntnis der Substitutionsprodukte der (2H)-Imidazol-4(3H)-thione und 2H-Imidazol-4(3H)-one

2H-Imidazole-4(3H)-thiones (a), available from methyl alkyl and methyl aryl ketones with sulfur and ammonia, react via their corresponding N-sodium compounds or in presence of tert. amines with alkyl and aryl carboxylic acid chlorides to give the corresponding intensely coloured (orange to violett) cryst. 3-acyl-2H-imidazole-4(3H)-thiones4 a-q and6–26. With dicarboxylic acid dichlorides the colourless cryst. N,N′-diacyl-bis-3-imidazoline-5-thiones5 a-d and27–32 are obtained. With carbamic acid chlorides and chloroformic acid esters the corresponding urea (33–35) and urethane derivatives36, 37 are formed. In an analogous way 2H-imidazol-4(3H)-ones react with acid chlorides to 3-acyl-2-imidazol-4(3H)-ones (44–50), which can also be obtained by treating the corresponding 3-acyl-2H-imidazole-4(3H)-thione with KMnO₄.     

Activated Monomers and Nucleophilic Reagents in Addition and Polymerization Reactions

A number of examples of addition and polymerization reactions is presented with special emphasis on the chemical behaviors of activated monomers and/or activated nucleophilic reagents. Lithium alkoxyethanolate forms a complex with lithium alkyl. Spectroscopic studies showed this complex to possess agent-separated ion pairs. The nature of the complex is characterized by the enhanced reactivity of styrene in the copolymerization reaction with butadiene initiated by the complex. Magnesium alkyl can be sufficiently activated by magnesium alkoxyethanolate to polymerize styrene and diene. Aluminum alkyl and zinc alkyl are able to induce the anionic polymerization of vinyl ketones, but not of unsaturated esters or nitriles. Aluminum or zinc alkoxyethanolates fail to activate their corresponding metal alkyls. Bipyridyl, sparteine, triphenylphosphine, HMPT, and related Lewis bases, however, activate aluminum alkyl enough to react with carbon-carbon double bonds of the unsaturated esters and nitriles. Crotononitrile can be polymerized by the AIR₃-HMPT system to form a colorless polymer, where possible side reactions between CN and AIR₃ are prevented by HMPT. Mutual activation through complex formation is confirmed by a model system of a vinyl ketone with organozinc compounds. AIR₃-HMPT does not polymerize vinyl ketones because of a lack of complex formation. N-Carboxy-α-alanine anhydride (NCA) can be polymerized with zinc alkyl as initiator. The formation of activated NCA by proton abstraction from the NH group is shown to be the essential stage for polymerization. Zinc alkyl is also activated by conventional acid anhydrides. The propylene oxide ring can be cleaved with the ZnR₂-phthalic anhydride system, which is the initiation step in the alternate copolymerization between propylene oxide and the acid anhydride. The propagation mechanism of the CO₂-epoxide copolymerization is also discussed.     

Komplexchemie und Mechanismen metallkatalysierter CC-Kupphmgsreaktionen: III. Phosphol-Komplexe des nullwertigen Palladiums

Two equivalents of 1,2,5-triphenylphosphole (tpphol, 1) react with bis(dibenzylideneacetone)palladium(0), Pd(dba)₂ (2), to give the bis(phosphole) complex (tpphol)₂Pd(dba) (3). An excess of 1 displaces the remaining dba ligand, thus leading to the tris(phosphole) complex (tpphol)₃Pd (4). 3 reacts with chloroform to give trans-(tpphol)₂PdCl₂ (5). While the structurally characterized compound 4 is stable against chloroform, it reacts slowly with iodine to give the palladium(II) complex cis-(tpphol)₂PdI₂ (6).     

Substitution at C-4 in 3,5-disubstituted 4H-1,2,6-thiadiazin-4-ones

3,5-Diaryl-4H-1,2,6-thiadiazin-4-ones react with NaBH₄ to give the 3,5-diaryl-4H-1,2,6-thiadiazin-4-ols and with MeLi to give 4-methyl-3,5-diaryl-4H-1,2,6-thiadiazin-4-ols. The latter dehydrate with p-toluenesulfonic acid to give (3,5-diarylthiadiazin-4-ylidene)methanes. (3,5-Diphenyl-4H-1,2,6-thiadiazin-4-ylidene)methane 15 suffers mono bromination with NBS to give bromo(3,5-diphenyl-4H-1,2,6-thiadiazin-4-ylidene)methane 17. Dichloro- and dibromo(3,5-diphenyl-4H-1,2,6-thiadiazin-4-ylidene)methanes 18 and 19 are formed directly from the 3,5-diphenylthiadiazin-4-one 9 via the Appel reaction using Ph₃P and CCl₄ or CBr₄, respectively. 3,5-Diarylthiadiazin-4-ones treated with P₂S₅ give 3,5-diarylthiadiazine-4-thiones that react with tetracyanoethylene oxide to give the (thiadiazin-4-ylidene)malononitriles. Finally, the 3,5-diphenylthiadiazine-4-thione 20 reacts with ethyl diazoacetate to give ethyl 2-(3,5-diphenyl-4H-1,2,6-thiadiazin-4-ylidene)acetate 26. The above reactions show that a variety of substitutions at C-4 of 3,5-diaryl substituted 1,2,6-thiadiazin-4-ones can be achieved, which extends the potential applications of this heterocycle. All compounds are fully characterized and a brief comparison of their spectroscopic properties is given.     

Structure and reactivity of mono- and dinuclear diiminate zinc alkyl complexes

The synthesis, structure and reactivity of several diiminate ligands are presented. The syntheses of five representative β-diiminate (BDI) zinc alkyl complexes and one β-oxo-δ-diiminate (BODDI) zinc alkyl are described. BDI ligands with varying backbone and N-aryl substituents display different solid state structures. [(BDI)ZnR] are synthesized by the reaction of (BDI)H with ZnR₂ in quantitative yield. Previously reported (BDI-1)ZnEt is a three-coordinate monomer in the solid state whereas [(BDI-3)ZnEt]_∞ [(BDI-3)=2-((2,6-diisopropylphenyl)amido)-3-cyano-4-((2,6-diisopropylphenyl)imino-2-pentene] and [(BDI-4)ZnEt]_∞ [(BDI-4)=2-((2,6-diethylphenyl)amido)-3-cyano-4-((2,6-diethylphenyl)imino-2-pentene] form one dimensional coordination polymers. The bimetallic complex [(BODDI-1)(ZnEt)₂] [(BODDI-1)=2,6-bis((2,6-diisopropylphenyl)amido)-2,5-heptadien-4-one] is prepared through the reaction of (BODDI-1)H₂ with two equivalents ZnEt₂. Both [(BDI)ZnEt] and [(BODDI)ZnEt] complexes react with acetic acid to give the acetate complexes in moderate to high yields, offering a superior synthetic route to these complexes. [(BDI)ZnR] [BDI=(BDI-3) or 1,1,1-trifluoro-2-((2,6-diisopropylphenyl)amido)-4-((2,6-diethylphenyl)imino-2-pentene), (BDI-5)] complexes react with MeOH to produce [{(BDI)Zn(μ-OMe)}₂Zn(μ-OMe)₂] in moderate yields. The molecular structures of [(BDI-3)ZnEt], [(BDI-4)ZnEt], [(BODDI-1)(ZnEt)₂], [(BODDI-1)Zn₂(μ-OAc)₂], [{(BDI-3)Zn(μ-OMe)}₂Zn(μ-OMe)₂] and [{(BDI-5)Zn(μ-OMe)}₂Zn(μ-OMe)₂] have been determined by X-ray diffraction.     

Factors controlling the regioselectivity of additions to α-enones—III: Reactions of 3-aryl α-enones with phosphorylated anions

Reaction of phosphonoester 2 and phosphononitrile 3 with chalcone and p-methoxychaleone in THF-t-BuOK at room temperature gives only the product resulting from CC double bond attack. The same reagents with benzalacetone lead to mixture of products resulting from CC double bond and carbonyl attack, though phosphine oxide 4 gives only the products of CC attack. Dypnone gives products of carbonyl attack with 3 and does not react with 2.These results are discussed in terms of perturbation theory: C₄ attack increases with delocalization of the reagent's negative charge and lowering of the α-enone LUMO level.     

A new anilido-imine compound containing o-OMe-anilinyl derived from an unexpected adduct: Synthesis,crystal structure and its coordination capability

A new compound, ortho-C₆H₄F[CH(NHC₆H₄OMe-2)₂], 1, was obtained with ortho-flurobenzaldehyde and 2-methoxyaniline as the starting materials. Compound 1 was readily converted into ortho-C₆H₄(2-OMeC₆H₄)(CHNC₆H₄OMe-2) 2 after treatment with 1 equiv of n-BuLi. Treatment of compound 2 with 1.5 equiv of ZnEt₂ afforded the trinuclear zinc complex 3 by alkyl elimination and alkylation of the imino group of the ligand. The molecular structures of two new organic compounds and of the trinuclear zinc complex were determined by single-crystal X-ray diffraction. The dianionic ONNO tetradentate ligands derived from compound 2 coordinate to zinc ions in four to five coordination modes, forming distorted tetrahedral and trigonal–bipyramidal geometry around three metal centers.     

Characterization and pharmacological evaluation of new pyridine analogs

Reaction of 5-ethyl pyridine-2-ethanol 1 and methane sulphonyl chloride gives corresponding sulphonate 2; which on condensation with p-hydroxy benzaldehyde will give 4-[2-(5-ethylpyridin-2-yl)ethoxy]benzaldehyde 3. A series of chalcones 4a–o were prepared from 3 and substituted aromatic acetophenone. Chalcones 4a–o further react with guanidine nitrate to give a series of pyrimidines 5a–o which condense with 3,4-dichlorobenzylchloride to give amide derivatives 6a–o. Newly synthesized compounds have been examined on the basis of spectral analysis. All the compounds were screened against different gram-positive and gram-negative bacteria. Most of these compounds showed better inhibitory activity in comparison with the standard drugs.     

Komplexe des 2-(Trimethylsiloxy)phenylisocyanids als Vorstufen für die Darstellung von N,O-Heterocarben-Komplexen

The reaction of 2-(trimethylsiloxy)phenylisocyanide 1 with PdI₂ or CoI₂ leads to the square-planar complex trans-[Pd(l)₂I₂] 2 and the octahedral complex trans-[CO(1₄I₂] 3, respectively. Both 2 and 3 were characterized by X-ray structure analysis. Cleavage of the Si-O bond gives complexes with coordinated 2-hydroxyphenylisocyxanide ligands which rearrange via an intramolecular nucleophilic attack of the hydroxyl oxygen at the isocyanide carbon to give complexes with cyclic N,O-heterocarbene ligands.     

Synthesis and catalytic activity of DI-μ-methoxo-bis[(2-aminopyridine)(chloro)copper(II)] and m-xylylenediamine Zn(OAc)2

Compound I, [di-μ-methoxo-bis[(2-aminopyridine)(chloro)copper(II)], was obtained by two different synthetic routes. In synthetic route 1, we first obtained intermediate by the addition of two equivalents of o-aminopyridine to copper chloride in an ethanolic solution, and then we recrystallized the intermediate from methanol and n-hexane to give compound I. Synthetic route 2 involved the reaction of o-aminopyridine with copper chloride in a methanol solution directly. The crystal structure of compound I was obtained. The reaction of m-xylylenediamine with Zn(OAc)₂ · 2H₂O in THF resulted in the production of one novel zinc complex C₁₂H₁₈N₂O₄Zn, bis(m-xylenediamine)zinc (II) and its structure was determined by X-ray diffraction analysis. Complexes I and II were also characterized by elemental analysis, and IR. Then they were applied as catalysts for the Henry reaction, and they achieved good conversions (64 and > 99%, respectively).     

Thioimidazolate versus pyrazolate-zinc(II)-bound hydroxo complex as structural model for the active site of hydrolytic enzyme: the crystal structure of the inclusion complex TtZn–O–C6H4–p-NO2, Tt?=?hydrotris(N-xylyl-2-thioimidazolyl)borate

The reaction of the tripod ligand hydrotris(N-(2-methylphenyl)-2-thioimidazol-1-yl)borate, Tt with zinc(II) chloride yielded the chloro complex [TtZn–Cl] 1. The hydrolytic reactivity of its hydroxo complex [TtZn–(μ-OH)ZnTt]Cl 2 towards p-nitrophenyl acetate was hampered due to the formation of the stable phenolate complex [TtZn–O–Ar–p-NO₂] 3 as a product inhibition. The X-ray structure analysis of complex 3 was determined and showed that its Zn[S₃O] coordination sphere includes three thione donors from the ligand Tt and one oxygen donor from the hydrolysed product p-nitrophenolate in an ideally tetrahedral arrangement around the zinc(II) centre.     

Cleavage of cyclopropene ring by means of transition metal salts

The oxidative ring cleavage of 1,3,3-trimethylcyclopropene (1) with Hg(OAc)₂ in methylene chloride gives 1,1-diacetoxy-2,3-dimethyl-2-butene (5). The reaction of 1 with TI(OAc)₃ or Pb(OAc)₄ gives in addition to 5, 3,3-diacetoxy-2-methylpropene and 2-acetoxy-4-methyl-1,3-pentadiene. These products are explained by assuming the addition of metal acetates onto the double bond of 1 followed by the ring cleavage to give vinylcarbene-metal acetate complexes or inverse ylides. The reaction of benzocyclopropene (14) with Hg(OAc)₂ affords bis(o-acetoxymethylphenyl)mercury as a single product. Cyclopropene ring cleavage of 14 effected by Cu(II) or Ag(l) acetate furnishes 9,10-dihydrophenanthrene and benzyl acetate. These products are ascribed to the intermediary vinylcarbene- metal acetate complexes produced from 14.     

Cyclometallated imine complexes with oxygen-functionalised side-chains: Effect of the nature of the functional group, chain length and charge on coordination of the oxygen

Imines 1a-e derived from benzaldehyde or 3,4-dimethoxy benzaldehyde and ether- or alcohol-functionalised amines H₂NR (R = C₂H₄OMe, C₃H₆OMe, C₂H₄OH, C₃H₆OH,) all undergo cyclometallation with [Pd(OAc)₂]₃ (in some cases the dimeric products 2 were isolated) and subsequently react with lithium chloride to give chloride complexes, which are dimeric 3a-c, or monomeric for the C₃H₆OH-functionalised complexes 4d,e which have a C,N,O tridentate imine. The chloride complexes subsequently react with triphenylphosphine, and in some cases pyridine, to give mononuclear complexes 5 and 6, respectively with bidentate C,N imines. Treatment of 5 with silver salts leads to cations, the length of the tether (C2 or C3) and nature of the donor (ether or alcohol) and the counterion all effect whether or not the oxygen is coordinated.     

Carbonylation of aryl- and vinyl-tellurium compounds with carbon monoxide in the presence of palladium(II) salts

Aryl- and vinyl-tellurium(II or IV) compounds react with carbon monoxide (CO) in suitable organic solvents to give the corresponding carboylic acids in moderate to quantitative yields in the presence of a stoichiometric amount of a palladium(II) salt. Treatment of (Z)-styrylphenyl telluride with atmospheric pressure of CO at room temperature in the presence of palladium(II) chloride or lithium chloropalladate(II) affords predominantly (E)-cinnamic acid, while in the presence of palladium(II) acetate similar reaction gives the (Z)-acid highly selectively. Under higher CO pressures (5–50 atm), however, the (Z)-acid becomes the major product, even when palladium(II) chloride is used. The following pathways are proposed for this carbonylation: (1) in the first step organotellurium compounds form the monomeric and/or dimeric palladium complexes such as [(R₂Te)PdCl₂]₂ and/or (R₂Te)₂PdCl₂ (R = aryl, vinyl), then (2) the migration of R moiety from tellurium to palladium (transmetallation) occurs to afford the reactive aryl- or alkenyl-palladium compounds, and (3) the compounds react with CO to give the corresponding acylpalladium compounds, after alkaline hydrolysis, the carboxylic acids are formed. The presence of an ionic carbene-like organopalladium complex is proposed for the formation of the (Z)-acid from (Z)-telluride.     

Design and synthesis of novel perfluoroalkyl-containing zinc pyrithione biocide

Novel perfluoroalkyl-containing zinc pyrithione biocide 2 was designed and synthesized in six steps. Reaction of 4-methyl-pyridine with C₈F₁₇(CH₂)₃I in the presence of LDA followed by further oxidization of the resultant pyridine derivative 6 gave the pyridine N-oxide 9. Treatment of 9 with phosphorous oxychloride afforded the desirable chloride 12. Oxidization of compound 12 with H₂O₂ gave N-oxide 14, which was treated with NaSH to give the sulfide 3. Finally, treatment of compound 3 with NaOH/ZnSO₄ smoothly delivered perfluoroalkyl-containing zinc pyrithione biocide 2 in good yield.     

Syntheses and crystal structures of manganese,nickel and zinc chloride complexes with dimethoxyethane and di(2-methoxyethyl) ether

Reactions of manganese and zinc chloride with dimethoxyethane (DME) in the presence of (CH₃)₃SiCl and water resulted in [MnCl₂(DME)]_n (1) with a polymeric chain structure and in the molecular [ZnCl₂(DME)]₂ (2), respectively. The complexes 1 and 2 reacted with di(2-methoxyethyl) ether (abbreviated diglyme) in tetrahydrofuran (THF) solvent achieving binuclear [MnCl₂(diglyme)]₂ (3) and mononuclear [ZnCl₂(diglyme)] (4), respectively. The complex [NiCl₂(diglyme)]₂ (5) was prepared by the reaction of nickel chloride hexahydrate, diglyme and (CH₃)₃SiCl in THF solvent. A distorted octahedral geometry was found for manganese and nickel ions in the complexes 1, 3 and 5. Linear chains of manganese ions linked by double chloride bridges are present in 1. Two bridging chlorides connect two manganese or nickel atoms into isostructural binuclear molecules 3 and 5, respectively. Two zinc ions in the complex 2 are in different environments, in a tetrahedral and in an octahedral one, while five-coordinate zinc ions are present in the mononuclear complexes 4.     

Asymmetric hydrogenation of aromatic ketones using polymeric catalyst prepared from polymer-supported 1,2-diamine

tert-Butyloxycarbonyl (Boc) protected chiral 1,2-diamine monomers 3 were copolymerized with achiral vinyl monomers such as styrene, methacrylates, acrylates, methacrylamide, and acrylamide to give crosslinked polymers P2 containing chiral 1,2-diamine moieties. Deprotection of the Boc groups in the polymer afforded the crosslinked chiral 1,2-diamine polymer P3. The diamine polymer was allowed to react with RuCl₂/BINAP in DMF to form polymeric complex. Asymmetric hydrogenation of aromatic ketones smoothly proceeded using the polymeric complex to give the corresponding secondary alcohol in quantitative yield with high level of enantioselectivity up to 98% ee in a mixed solvent of DMF and 2-propanol. The polymeric catalyst can be recycled several times without loss of the activity.