Synthese und Eigenschaften von [Ph2(Carb)P]AlCl4 (Carb = 2,3‐Dihydro‐1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐yliden) – ein stabiler Carben‐Komplex des dreiwertigen Phosphors [1]

Synthesis and Properties of [Ph₂(Carb)P]AlCl₄ (Carb = 2,3‐Dihydro‐1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene) – a Stable Carbene Complex of Trivalent Phosphorus [1] 2,3‐Dihydro‐1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene ( 7 , Carb) reacts with chlorodiphenylphosphane to give the cationic phosphane [Ph₂(Carb)P]Cl ( 10 ) which is transferred to the more stable salt [Ph₂(Carb)]AlCl₄ ( 13 ) on treatment with AlCl₃. The cationic phosphane selenide [Ph₂(Carb)PSe]AlCl₄ ( 14 ) is obtained from 13 and selenium. Spectroscopic and structural data indicate [Ph₂(Carb)P]⁺ to be a cationic analogue of Ph₃P. The X‐ray structure of 13 is reported.     

Reaction of tellurium tetraiodide with 2,3‐dihydro‐1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene

2,3‐Dihydro‐1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene 1 (Carb, R¹ = ⁱPr, R² = Me) reacts with TeI₄ to give the carbene adduct CarbTeI₂ ( 3 ). The crystal structure of 3 consists of T‐shaped monomeric fragments linked by weak Te. I interactions to form infinite helical chains. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:316–319, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20090     

New Aspects of 1,3‐Diphosphacyclobutane‐2,4‐diyls

1,3‐Di(tert‐butyl)‐2,4‐bis[2,4,6‐tri(tert‐butyl)phenyl]‐1,3‐diphosphacyclobutane‐2,4‐diyl was formed from [2,4,6‐tri(tert‐butyl)phenyl]phosphaacetylene and t‐BuLi. In addition, the X‐ray diffraction analysis was carried out, together with theoretical calculations of the structure and NMR data.     

Synthese,Struktur, Elektrochemie und optische Eigenschaften von alkinylfunktionalisierten 1,3,2‐Diazaborolen und 1,3,2‐Diazaborolidinen

Syntheses, Structures, Electrochemistry and Optical Properties of Alkyne‐Functionalized 1,3,2‐Diazaboroles and 1,3,2‐Diazaborolidenes The reaction of 2‐bromo‐1,3‐ditert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazaborole ( 3 ) with lithiated tert‐butyl‐acetylene and lithiated phenylacetylene affords the 2‐alkynyl‐functionalized 1,3,2‐diazaboroles 4 and 5 as a thermolabile colorless oil ( 4 ) or a solid ( 5 ). Similarly 2‐bromo‐1,3‐diethyl‐2,3‐dihydro‐1H‐1,3,2‐benzodiazaborole ( 6 ) was converted into the crystalline 2‐alkynyl‐benzo‐1,3,2‐diazaboroles 7 and 8 by treatment with LiC≡C–tBu or LiC≡CPh, respectively. 2‐Ethynyl‐1,3‐ditert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazaborole ( 2 ) was metalated with tert‐butyl‐lithium and subsequently coupled with 2‐bromo‐1,3,‐ditert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazaborole ( 3 ) to afford bis(1,3‐ditert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazaborol‐2‐yl)acetylene ( 9 ) as thermolabile colorless crystals. Analogously coupling of the lithiated species with 6 or with 2‐bromo‐1,3‐ditert‐butyl‐1,3,2‐diazaborolidine ( 11 ) gave the unsymmetrically substituted acetylenes 10 or 12 , respectively, as colorless solids. Compounds 4 , 5 , 7 – 10 and 12 are characterized by elemental analyses and spectroscopy (IR, ¹H‐, ¹¹B{¹H}, ¹³C{¹H}‐NMR, MS). The molecular structures of 5 , 8 and 9 were elucidated by X‐ray diffraction analyses.     

5,5′‐Di‐tert‐butyl‐2,2′‐di­hydroxy‐3,3′‐methyl­enedibenz­aldehyde and 6,6′‐di‐tert‐butyl‐8,8′‐methyl­ene­bis­(spiro­[4H‐1,3‐benzodioxin‐2,1′‐cyclo­hexane])

Two related compounds containing p‐tert‐butyl‐o‐methyl­ene‐linked phenol or phenol‐derived subunits are described, namely 5,5′‐di‐tert‐butyl‐2,2′‐di­hydroxy‐3,3′‐methyl­ene­di­benz­aldehyde, C₂₃H₂₈O₄, (I), and 6,6′‐di‐tert‐butyl‐8,8′‐methyl­ene­bis­(spiro­[4H‐1,3‐benzo­di­oxin‐2,1′‐cyclo­hexane]), C₃₅H₄₈O₄, (II). Both compounds adopt a `butterfly' shape, with the two phenol or phenol‐derived O atoms in distal positions. Phenol and aldehyde groups in (I) are involved in intramolecular hydrogen bonds and the two dioxin rings in (II) are in distorted half‐chair conformations.     

Synthesis of p‐tert‐Butyl‐calix[6] ‐biscrown‐3 via Intramolecular Ring‐closure of 1,4‐Bis (2‐(2‐chloroethoxy) ethoxy) ‐p‐tert‐butyl‐calix[6]arene

With a variation in reaction conditions, 1, 4‐bis (2‐(2‐chloroethoxy)ethoxy)‐calix[6]arene (3) and l,3,5‐tris(2‐(2‐chloroethoxy) ethoxy)‐calix [6] arene (4) or 4 and 4‐chloroethoxyethoxy‐calix[6]crown‐3 (5) were selectively synthesized from p‐tert‐butyl‐calix [6] arene and 2‐(2‐chloroethoxy)ethyltosylate. l,3–4,6‐p‐tert‐butylcalix[6]‐bis‐crown‐3 (6) with (u,u,u,d,d,d) conformation and 1,3–4,5‐p‐tert‐butylcalix[6]‐biscrown‐3 (7) with self‐anchored (u,u, u, u, u, d) conformation were synthesized through an intramolecularly ring‐closing condensation of 1, 4‐bis (2‐(2‐chloroethoxy)ethoxy)‐p‐tert‐butyl‐calix[6]arene (3) in 25% and 15% yield, respectively. Using 5 instead of 3, only 7 was obtained in 65% high yield. 6 and 7 show different complexation properties toward alkali metal and ammonium ions.     

Wasserstoffbrückenbindungen mit Cyanidionen? Die Strukturen von 1,3‐Diisopropyl‐4,5‐dimethylimidazoliumcyanid und 1‐Isopropyl‐3,4,5‐trimethylimidazoliumcyanid

Hydrogen Bonds with Cyanide Ions? The Structures of 1,3‐Diisopropyl‐4,5‐dimethylimidazolium Cyanide and 1‐Isopropyl‐3,4,5‐trimethylimidazolium Cyanide 1,3‐Diisopropyl‐4,5‐dimethylimidazolium cyanide ( 2a ) and 1‐isopropyl‐3,4,5‐trimethylimidazolium cyanide ( 2b ) are obtained from the reaction of the corresponding 2,3‐dihydrodimethylimidazol‐2‐ylidenes ( 1 ) and hydrogen cyanide in excellent yield. Their crystal structure analyses reveal the presence of ion pairs linked by hydrogen bonds. The crystal structure analysis of 2a reveals a near colinear orientation of the C(1)‐H bond axis and the cyanide ion while in 2b this orientation is perpendicular. In both cases, the interionic distances are in the expected range for hydrogen bonds. Ab‐initio calculations of the total energy of the salts 2 indicate small differences in energy between the colinear and perpendicular orientation of the ions as well as between the colinear C‐H···C‐N and C‐H···N‐C orientations. The comparison of calculated and measured ¹³C and ¹⁵N NMR chemical shifts does not allow the distinction between the possible orientations.     

Synthese und Struktur von 1,3‐Diisopropyl‐4,5‐dimethylimidazolium‐2‐sulfonat: Ein Carbenaddukt des Schwefeltrioxids

Synthesis and Structure of 1,3‐Diisopropyl‐4,5‐dimethylimidazolium‐2‐sulfonate: A Carbene Adduct of Sulfur Trioxide [1] The stable betaine 1,3‐diisopropyl‐4,5‐dimethylimidazolium‐2‐sulfonate ( 5 ) is obtained through hydrolysis of the 2‐chloro‐1,3‐diisopropyl‐4,5‐dimethylimidazolium chloro‐ sulfite salt ( 4 b ) in the presence of cyanide. The crystal structure analysis of 5 is reported.     

A New Class of Organosuperbases,N‐Alkyl‐ and N‐Aryl‐1,3‐dialkyl‐4,5‐dimethylimidazol‐2‐ylidene Amines: Synthesis,Structure, pKBH+ Measurements,and Properties

A series of stable organosuperbases, N‐alkyl‐ and N‐aryl‐1,3‐dialkyl‐4,5‐dimethylimidazol‐2‐ylidene amines, were efficiently synthesized from N,N′‐dialkylthioureas and 3‐hydroxy‐2‐butanone and their basicities were measured in acetonitrile. The derivatives with tert‐alkyl groups on the imino nitrogen were found to be more basic than the tBu P₁ (pyrr) phosphazene base in acetonitrile. The origin of the high basicity of these compounds is discussed. In acetonitrile and in the gas phase, the basicity of the alkylimino derivatives depends on the size of the substituent at the imino group, which influences the degree of aromatization of the imidazole ring, as measured by ¹³C NMR chemical shifts or by the calculated ΔNICS(1) aromaticity parameters, as well as on solvation effects. If a wider range of imino‐substituents, including electron‐acceptor substituents, is treated in the analysis then the influence of aromatization is less predominant and the gas‐phase basicity becomes more dependent on the field‐inductive effect, polarizability, and resonance effects of the substituent.     

Diastereoselective Synthesis of (Z)‐6‐(2‐Oxo‐1,2‐dihydro‐3H‐indol‐3‐ylidene)‐3,3a,9,9a‐tetrahydroimidazo[4,5‐e]thiazolo[3,2‐b]‐1,2,4‐triazin‐2,7(1H,6H)‐diones

Two efficient and diastereoselective procedures for the synthesis of (Z)‐6‐(2‐oxo‐1,2‐dihydro‐3H‐indol‐3‐ylidene)‐3,3a,9,9a‐tetrahydroimidazo[4,5‐e]thiazolo[3,2‐b]‐1,2,4‐triazin‐2,7(1H,6H)‐diones by aldol‐crotonic condensation of 1,3‐dimethyl‐3a,9a‐diphenyl‐3,3a,9,9a‐tetrahydroimidazo[4,5‐e]thiazolo[3,2‐b]‐1,2,4‐triazin‐2,7(1H,6H)‐dione with isatins under acidic or basic catalysis are reported. Isomerization in (Z)‐7‐(1‐allyl‐2‐oxo‐1,2‐dihydro‐3H‐indol‐3‐ylidene)‐1,3‐dimethyl‐3a,9a‐diphenyl‐1,3a,4,9a‐tetrahydroimidazo[4,5‐e]thiazolo[2,3‐c]‐1,2,4‐triazin‐2,8(3H,7H)‐dione was observed under basic conditions.     

Preparation of substituted 1,3‐dihydro‐2H‐imidazo[4,5‐c]pyridin‐2‐ones

A new synthetic route to 6‐substituted‐imidazo[4,5‐c]pyridin‐2‐ons from 4‐aminopyridine has been investigated. 4‐Aminopyridine protected as alkyl carbamates were nitrated with dinitrogen pentoxide to the corresponding methyl, i‐propyl and t‐butyl 3‐nitropyridin‐4‐yl carbamates ( 5a‐c ) in 51‐63 % yields. Attempts to substitute these in the 6‐position by the ONSH and the VNS techniques succeeded with butyl‐amine and the t‐butyl carbamate 9 . From the methyl or t‐butyl 3‐nitropyridin‐4‐yl carbamates 5a, 5c 1,3‐dihydro‐2H‐imidazo[4,5‐c]pyridin‐2‐one ( 1 ) was formed in 73 and 39 % yields, respectively. t‐Butyl 6‐N‐butylamin‐3‐aminopyridin‐4‐yl carbamate ( 6 ) gave 6‐butylamino‐1,3‐dihydro‐2H‐imidazo[4,5‐c]‐pyridin‐2‐one (7) in 53 % yield.     

Synthesis and Fungicidal Activities of 2,3‐Dimethyl‐4‐(1‐acyloxy)alkoxy‐6‐tert‐butyl‐8‐fluoroquinolines

A series of 2,3‐dimethyl‐4‐(1‐acyloxy)alkoxy‐6‐tert‐butyl‐8‐fluoroquinolines were synthesized by 4‐(tert‐butyl)aniline as the starting material via acylation, substitution, and hydrolysis, and their structures were characterized by ¹H NMR, ¹³C NMR, and HRMS. The fungicidal activity showed that compounds 6c , 6e , and 6f had excellent activity against Sphoaerotheca fuliginea with EC₅₀ values of 38.62, 6.77, and 50.35 mg/L, respectively. The results suggest that this chemotype of compounds warrant further studies as promising fungicide.     

Catenation of 1,3‐Diphosphacyclobutane‐2,4‐diyl Units Having 2,4,6‐Tri‐tert‐butylphenyl Protecting Groups and a P‐sec‐Butyl Group in the Ring

Two and three stable 1‐sec‐butyl‐2,4‐bis(2,4,6‐tri‐tert‐butylphenyl)‐1,3‐diphosphacyclobutane‐2,4‐diyl units were catenated to construct multi‐biradical derivatives by utilizing 1,3‐di‐, 1,4‐di‐, and 1,3,5‐trimethylenebenzenes as bridging groups, respectively. UV/Vis spectroscopic and cyclovoltammetric (CV) properties of the multi‐biradicals indicate a non‐conjugative interaction between the concatenated biradical units.     

2,4,6‐Tri‐tert‐butylphenyl and 2,4‐di‐tert‐butyl‐6‐methylphenyl groups: Look similar,react differently

The crystal structures of molecules with two phosphaalkene groups have been determined. Differences in the stabilization of the PC π‐bond by the 2,4,6‐tri‐tert‐butylphenyl and 2,4‐di‐tert‐butyl‐6‐methylphenyl groups were observed. It has been found that lithium supermesityl(trimethylsilyl)phosphide could be a very efficient base to remove a proton from acetonitrile.© 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:662–666, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10083     

Synthesis of dihydrothieno[2,3‐b]pyridines based on titanium(IV) chloride‐mediated michael reactions of 2‐amino‐4,5‐dihydro‐3‐thiophenecarbonitriles with α,β‐unsaturated ketones

2‐Arnino‐4,5‐dihydro‐3‐thiophenecarbonitriles 1a‐c reacted with α,β‐unsaturated ketones (e.g. methyl vinyl ketone 2 and benzalacetone 3 ) in the presence of titanium(IV) chloride to give the corresponding Michael adducts 4a‐c and 5a‐c. Thermal treatment of compounds 4a‐c and 5a‐c with titanium(IV) chloride caused intramolecular cyclocondensation to yield the corresponding tetrahydrothieno[2,3‐b]pyridines 6a‐c and 7a‐c. Aromatization of 6a‐c and 7a‐c with potassium tert‐butoxide in refluxing tert‐butyl alcohol pro ceeded smoothly to afford the corresponding dihydrothieno[2,3‐b]pyridines 8a‐c and 9a‐c.     

New Lipophilic 2‐Amino‐N,N′‐dialkyl‐4,5‐dimethylimidazolium Cations: Synthesis,Structure, Properties,and Outstanding Thermal Stability in Alkaline Media

A series of new N,N′‐dialkyl‐4,5‐dimethylimidazolium cations possessing electron‐rich 2‐imidazolylidene‐ or phosphoranylidene‐amino substituents has been efficiently synthesized from common precursors, N,N′‐dialkyl‐4,5‐dimethylimidazol‐2‐ylidenes. The new lipophilic salts obtained have been found to be highly stable towards strong alkali under both biphasic and homogeneous conditions. Their exceptional aqueous base resistance, which has hitherto only been seen with peralkylated polyaminophosphazenium cations, may be attributed to three factors: aromatic stabilization, efficient resonance charge delocalization, and steric protection of the exocyclic nitrogen linkage due to bulky lipophilic N‐alkyl substituents.     

The antioxidant methyl 3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propionate

The title compound, C₁₈H₂₈O₃, was prepared by the reaction of 2,6‐di‐tert‐butylphenol with methyl acrylate under basic conditions using dimethyl sulfoxide as the promoter. The structure of this antioxidant indicates significant strain between the ortho tert‐butyl substituents and the phenolic OH group. In spite of the steric crowding of the OH group, it participates in intermolecular hydrogen bonding with the ester carbonyl O atom.     

The absolute configuration of (2S,4S)‐ and (2R,4R)‐2‐tert‐butyl‐4‐methyl‐3‐(4‐tolyl­sulfon­yl)‐1,3‐oxazolidine‐4‐carbaldehyde

The title enanti­omorphic compounds, C₁₆H₂₃NO₄S, have been obtained in an enanti­omerically pure form by crystallization from a diastereomeric mixture either of (2S,4S)‐ and (2R,4S)‐ or of (2R,4R)‐ and (2S,4R)‐2‐tert‐butyl‐4‐methyl‐3‐(4‐tolyl­sulfon­yl)‐1,3‐oxazolidine‐4‐carbaldehyde. These mixtures were prepared by an aziridination rearrangement process starting with (S)‐ or (R)‐2‐tert‐butyl‐5‐methyl‐4H‐1,3‐dioxine. The crystal structures indicate an envelope conformation of the oxazolidine moiety for both compounds.     

Eight 7‐benzyl‐3‐tert‐butyl‐1‐phenylpyrazolo[3,4‐d]oxazines,encompassing structures containing no intermolecular hydrogen bonds,and hydrogen‐bonded structures in one,two or three dimensions

7‐Benzyl‐3‐tert‐butyl‐1‐phenyl‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₂H₂₅N₃O, (I), and 3‐tert‐butyl‐7‐(4‐methylbenzyl)‐1‐phenyl‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₃H₂₇N₃O, (II), are isomorphous in the space group P2₁, and molecules are linked into chains by C—H...O hydrogen bonds. In each of 3‐tert‐butyl‐7‐(4‐methoxybenzyl)‐1‐phenyl‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₃H₂₇N₃O₂, (III), which has cell dimensions rather similar to those of (I) and (II), also in P2₁, and 3‐tert‐butyl‐1‐phenyl‐7‐[4‐(trifluoromethyl)benzyl]‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₃H₂₄F₃N₃O, (IV), there are no direction‐specific interactions between the molecules. In 3‐tert‐butyl‐7‐(4‐nitrobenzyl)‐1‐phenyl‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₂H₂₄N₄O₃, (V), a combination of C—H...O and C—H...N hydrogen bonds links the molecules into complex sheets. There are no direction‐specific interactions between the molecules of 3‐tert‐butyl‐7‐(2,3‐dimethoxybenzyl)‐1‐phenyl‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₄H₂₉N₃O₃, (VI), but a three‐dimensional framework is formed in 3‐tert‐butyl‐7‐(3,4‐methylenedioxybenzyl)‐1‐phenyl‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₃H₂₅N₃O₃, (VII), by a combination of C—H...O, C—H...N and C—H...π(arene) hydrogen bonds, while a combination of C—H...O and C—H...π(arene) hydrogen bonds links the molecules of 3‐tert‐butyl‐1‐phenyl‐7‐(3,4,5‐trimethoxybenzyl)‐6,7‐dihydro‐1H,4H‐pyrazolo[3,4‐d][1,3]oxazine, C₂₅H₃₁N₃O₄, (VIII), into complex sheets. In each compound, the oxazine ring adopts a half‐chair conformation, while the orientations of the pendent phenyl and tert‐butyl substituents relative to the pyrazolo[3,4‐d]oxazine unit are all very similar.     

Investigation of the Catalytic Activity of a 2‐Phenylidenepyridine Palladium(II) Complex Bearing 4,5‐Dicyano‐1,3‐bis(mesityl)imidazol‐2‐ylidene in the Mizoroki‐Heck Reaction

The phenylidenepyridine (ppy) palladacycles [PdCl(ppy)(IMes)] ( 4 ) [IMes = 1,3‐bis(mesityl)imidazol‐2‐ylidene] and [PdCl(ppy){(CN)₂IMes}] ( 6 ) [(CN)₂IMes = 4,5‐dicyano‐1,3‐bis(mesityl)imidazol‐2‐ylidene] were prepared by facile two step syntheses, starting with the reaction of palladium(II) chloride with 2‐phenylpyridine followed by subsequent addition of the NHC ligand to the precatalyst precursor [PdCl(ppy)]₂. Suitable crystals for the X‐ray analysis of the complexes 4 and 6 were obtained. It was shown that 6 has a shorter NHC‐palladium bond than the IMes complex 4 . The difference of the palladium carbene bond lengths based on the higher π‐acceptor strength of (CN)₂IMes in comparison to IMes. Thus, (CN)₂IMes should stabilize the catalytically active central palladium atom better than IMes. As a measure for the π‐acceptor strength of (CN)₂IMes compared to IMes, the selone (CN)₂IMes · Se ( 7 ) was prepared and characterized by ⁷⁷Se‐NMR spectroscopy. The π‐acceptor strength of 7 was illuminated by the shift of its ⁷⁷Se‐NMR signal. The ⁷⁷Se‐NMR signal of 7 was shifted to much higher frequencies than the ⁷⁷Se‐NMR signal of IMes · Se. Catalytic experiments using the Mizoroki‐Heck reaction of aryl chlorides with n‐butyl acrylate showed that 6 is the superior performer in comparison to 4 . Using complex 6 , an extensive substrate screening of 26 different aryl bromides with n‐butyl acrylate was performed. Complex 6 is a suitable precatalyst for para‐substituted aryl bromides. The catalytically active species was identified by mercury poisoning experiments to be palladium nanoparticles.