Activated sterically strained C=N bond in N-substituted p-quinone mono- and diimines: XIV. Reaction of some 3,5-dimethyl-1,4-benzoquinone monoimines with alcohols

Steric strain in the C=N-C fragment in 3,5-disubstituted N-acyl-1,4-benzoquinone monoimines, unlike their N-arylsulfonyl analogs, leads to increase of the C=N-C angle above 130° or twisting of the double C=N bond and loss of planarity of the quinoid ring. This structural transformation enhances the reactivity of the C=N bond so that 1,2-addition of alcohols becomes possible with formation of sterically unstrained cyclohexadienone structure with sp ³-hybridized C⁴ carbon atom.     

Halogenation of N-substituted p-quinone monoimines and p-quinone monooxime ethers: XIV. Halogenation of N-[arylsulfonylimino(phenyl)methyl]-2,5-dialkyl-1,4-benzoquinone monoimines and their reduction products

Despite steric hindrances created by the bulky substituent on the nitrogen atom, halogenation of 2,5-dialkyl-N-[arylsulfonylimino(phenyl)methyl]-1,4-benzoquinone monoimines fairly readily gives their derivatives having two halogen atoms in the quinoid ring.     

Reactions of <Emphasis Type="Italic">N</Emphasis>-aryl(methyl,trifluoromethyl)sulfonyl-1,4-benzoquinone monoimines with sodium sulfinates

In reactions with sodium sulfinates of N-substituted 1,4-benzoquinone monoimines with the quinoid ring having free positions 2 and/or 6 the fraction of products of 1,4-addition of the sulfinate ion grows in the series ArSO₂ → MeSO₂ → CF₃SO₂. In the case of 2,6-dimethyl derivatives the 1,6-addition is preferable, and the amount of products of 6,1-addition decreases.     

Halogenation of N-substituted p-quinone imines and p-quinone oxime esters: IV. Chlorination and bromination of N-arylsulfonyl-2(3)-methyl(2-chloro)-1,4-benzoquinone monoimines

The addition of halogens to N-arylsulfonyl-1,4-benzoquinone imines, which exist in a solution as Z and E isomers, is controlled by the steric factor. Z-E Isomerization strongly affects the stability of cyclohexene structures formed by halogenation of 1,4-benzoquinone imines. The halogenation of N-arylsulfonyl-1,4-benzoquinone imines was found to be accompanied by prototropic rearrangement.     

Synthesis and structure of N-alkyl(aryl)aminocarbonyl-1,4-benzoquinone imines

New N-alkyl(aryl)aminocarbonyl-1,4-benzoquinone imines were synthesized by reaction of isocyanates with the corresponding substituted 4-aminophenols, and their structure was determined on the basis of ¹H and ¹³C NMR spectra and X-ray diffraction data.     

Synthesis and structure of N-aryl(phenoxy, benzylidene)acetyl-1,4-benzoquinone monoimines

New N-aryl(phenoxy, benzylidene)acetyl-1,4-benzoquinone monoimines were synthesized by reaction of aminophenols with arylacetyl, phenoxyacetyl, and cinnamoyl chlorides in dimethylformamide-acetic acid (1: 3) in the presence of anhydrous sodium acetate. Structural parameters of the products and their probable biological activity were determined.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-alkyl(aryl)aminocarbonyl-1,4-benzoquinone monoimines with alcohols

Reactions of N-alkyl(aryl)aminocarbonyl-3,5-dimethyl-1,4-benzoquinone monoimines with alcohols led to the formation of products of 1,2-addition, quinolide compounds. They are the final products in reactions with alkyl derivatives, but in event of aryl derivatives they underwent cyclization with the subsequent elimination of the alcohol molecule to provide 4,7a-dimethyl-1-aryl-7,7a-dihydro-1H-benzimidazole-2,6-diones.     

Halogenation of N-substituted p-quinone monoimines and p-quinone monooxime esrers: XI. Synthesis and halogenation of 4-[aryl(alkyl)aminocarbonyl-oxyimino]cyclohexa-2,5-dien-1-ones

4-[Aryl(alkyl)aminocarbonyloxyimino]cyclohexa-2,5-dien-1-ones were synthesized by treatment of various substituted p-quinone monooximes with aryl isocyanates. The selectivity in the halogenation of the obtained p-quinone monooxime esters depended on the substrate structure and was either completely (syn addition) or partly regioselective (syn or anti addition). In all cases, the effect of steric factor was crucial, and the reaction was accompanied by halogenation of the aryl fragment.     

Activated sterically strained C=N bond in <Emphasis Type="Italic">N</Emphasis>-substituted <Emphasis Type="Italic">p</Emphasis>-quinone mono- and diimines: XV. Synthesis,structure, and reactions with alcohols of <Emphasis Type="Italic">N</Emphasis>-carbamoyl-1,4-benzoquinone imines

The reaction of 4-aminophenols with N-nitrourea or with sodium cyanate in acetic acid gave the corresponding 4-ureidophenols which were oxidized to N-carbamoyl-1,4-benzoquinone imines, substituted N-(4-oxocyclohexa-2,5-dien-1-ylidene)ureas. N-(2,6-Dimethyl-4-oxocyclohexa-2,5-dien-1-ylidene)urea possessing activated sterically strained C=N bond reacted with alcohols to afford N-(1-alkoxy-2,6-dimethyl-4-oxocyclohexa-2,5-dienyl)ureas.     

Modern synthetic methods for copper-mediated C(aryl)[bond]O, C(aryl)[bond]N, and C(aryl)[bond]S bond formation

The copper-mediated C(aryl)[bond]N, C(aryl)[bond]O, and C(aryl)[bond]S bond formation is an important transformation and has been developed to include a wide range of substrates. This Review highlights the recent developments in the copper-mediated (both stoichiometric and catalytic) reactions of aryl boronic acids, aryl halides, iodonium salts, siloxanes, stannanes, plumbanes, bismuthates, and trifluoroborate salts as aryl donors. In particular, the recent introduction of boronic acids as reaction partners in both O- and N-arylation has been a significant discovery and will occupy centre-stage in this review. Clear improvements can be obtained by the correct choice of copper source, base, ligands, and other additives. Mechanistic investigations should provide insight into the catalytically active species, which would aid in the development of milder, more-efficient methods.     

Synthesis and thiocyanation of <Emphasis Type="Italic">N</Emphasis>-alkyl(trifluoromethyl)sulfonyl 1,4-benzoquinone monoimines

New N-alkyl(trifluoromethyl)sulfonyl 1,4-benzoquinone monoimines were synthesized, and their thiocyanation gave 5-alkyl(trifluoromethyl)sulfonylamino-1,3-benzoxathiol-2-ones. An intermediate thiocyanation product, 5-trifluoromethylsulfonylamino-1,3-benzoxathiol-2-imine, was isolated for the first time.     

Halogenation of N-substituted para-quinone monoimines and para-quinone monoximes ethers: IX. Halogenation of N-aroyl-2,6(3,5)-dimethyl-1,4-benzoquinone monoimines and their reduced forms

At the halogenation of N-aroyl-2,6(3,5)-dimethyl-1,4-benzoquinone imines we found the halogenation of methyl groups to occur. The bromination of N-aroyl-2,6-dimethyl-1,4-benzoquinone imines yielded 3,6-dibromo-2,6-dimethyl-5-aroyloxycyclohex-2-ene-1,4-diones due to the strong acceptor property of the ArCO group and high redox potentials of N-aroyl derivatives. In the chlorination of N-aroyl-3,5-dimethyl-1,4-benzoquinone imines the chlorine addition to the C=C bond of the quinoid ring proceeded both by the trans- and syn-scheme.     

Halogenation of N-substituted p-quinone monoimines and p-quinone monooxime ethers: XIII. Specificity of bromination of N-Acetyl(aroyl)-1,4-benzoquinone monoimines

6-Hydroxy-2-methyl(aryl)-1,3-benzoxazoles were synthesized by bromination of N-acetyl(aroyl)-1,4-benzoquinone monoimines.     

Complexation of N-alkyl(aryl)- and N,N-dialkylcarbamoylmethylphosphine oxides with the f-elements

Complexation of N-alkyl(aryl)carbamoylmethylphosphine oxides (CMPO) and their N, N-dialkyl analogs in neutral media was studied. N-Alkyl derivatives react with praseodymium and europium nitrates both in solution and in the individual state to give 1: 2 and 1: 3 complexes, depending on the ratio of the starting reagents; for N-aryl amides, 1: 3 complexes were obtained only. With the uranyl cation, both N-alkyl and N,N-dialkyl derivatives of CMPO form various 1: 1 complexes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1856–1862, September, 2008.     

A class of luminescent cyclometalated alkynylgold(III) complexes: synthesis, characterization, and electrochemical, photophysical, and computational studies of [Au(C=N=C)(C triple bond C-R)] (C=N=C = kappa(3)C,N,C bis-cyclometalated 2,6-diphenylpyridyl)

A new class of luminescent cyclometalated alkynylgold(III) complexes, [Au(RC=N(R')=CR)(CCR' ')], i.e., [Au(C=N=C)(C triple bond CR')] (HC=N=CH = 2,6-diphenylpyridine) R' ' = C6H5 1, C6H4-Cl-p 2, C6H4-NO2-p 3, C6H4-OCH3-p 4, C6H4-NH2-p 5, C6H4-C6H13-p 6, C6H13 7, [Au(tBuC=N=CtBu)(C triple bond CC6H5)] 8 (HtBuC=N=CtBuH = 2,6-bis(4-tert-butylphenyl)pyridine), and [Au(C=NTol=C)(CCC6H4-C6H13-p)] 9 (HC=NTol=CH = 2,6-diphenyl-4-p-tolylpyridine), have been synthesized and characterized. The X-ray crystal structures of most of the complexes have also been determined. Electrochemical studies show that, in general, the first oxidation wave is an alkynyl ligand-centered oxidation, while the first reduction couple is ascribed to a ligand-centered reduction of the cyclometalated ligand with the exception of 3 in which the first reduction couple is assigned as an alkynyl ligand-centered reduction. Their electronic absorption and luminescence behaviors have also been investigated. In dichloromethane solution at room temperature, the low-energy absorption bands are assigned as the pi-pi* intraligand (IL) transition of the cyclometalated RC=N(R')=CR ligand with some mixing of a [pi(C triple bond CR') --> pi*(RC=N(R')=CR)] ligand-to-ligand charge transfer (LLCT) character. The low-energy emission bands of all the complexes, with the exception of 5, are ascribed to origins mainly derived from the pi-pi* IL transition of the cyclometalated RC=N(R')=CR ligand. In the case of 5 that contains an electron-rich amino substituent on the alkynyl ligand, the low-energy emission band was found to show an obvious shift to the red. A change in the origin of emission is evident, and the emission of 5 is tentatively ascribed to a [pi(CCC6H4NH2) --> pi*(C=N=C)] LLCT excited-state origin. DFT and TDDFT computational studies have been performed to verify and elucidate the results of the electrochemical and photophysical studies.     

Activated Sterically Strained C = N Bond in N-Arylsulfonyl-p-quinonemono- and Diimines: IX. Synthesis and Reactions of N-Tosyl-2,3,5,6-tetramethyl-1,4-benzoquinonimine

N-Tosyl-2'3'5'6-tetramethyl-1'4-benzoquinonimine as the other N-arylsulfonyl-1'4-benzo-quinonimines with an activated C = N bond reacts along 1'2-addition path with alcohols, sodium azideand along 1,2-addition-elimination path with aromatic amines. The higher activity of the C = N bond in theN-arylsulfonyl-1,4-benzoquinonimines is not due to the electronic character of the substituent attached to the ring (Cl, CH₃) but to steric influence resulting in increase in the bond angle C = N-S.     

(C(wedge)N(wedge)N)Pt(C identical to C)nR] (HC(wedge)N(wedge)N = 6-aryl-2,2'-bipyridine,n = 1-4, R = aryl,SiMe3) as a new class of light-emitting materials and their applications in electrophosphorescent devices

Tridentate cyclometalated platinum(II) complexes bearing sigma-alkynyl ligands exhibit tunable photoluminescence and enhanced stability during vacuum deposition; OLEDs based on these materials display orange to red electrophosphorescence with low turn-on voltages (approximately 4 V), maximum luminance approaching 10,000 cd m-2 and efficiency up to 4.2 cd A-1.     

Synthesis and crystal structures of isolable terminal aryl hexatriyne and octatetrayne derivatives: Ar-(C triple bond C)nH (n = 3, 4)

Unprecedented stability has been observed in terminal aryl hexatriyne and terminal aryl octatetrayne derivatives by judicious choice of a bulky, nonplanar headgroup [viz., 4-(3,6-di- tert-butyl- N-carbazolyl)phenyl] which hinders topochemical intermolecular interactions in the crystal lattice.     

Activated Sterically Strained C = N Bond in N-Substituted p-Quinonemono- and -diimines: X. Reactions of N-[N-Arylsulfonylbenz(acet)imidoyl]-3,5-dimethyl-1,4-benzoquinonimines with Alcohols

N-[N-Arylsulfonylbenz(acet)imidoyl]-3,5-dimethyl-1,4-benzoquinonimines react with alcohols to give the corresponding adducts at the activated CÍN bond. The adducts lose alcohol molecule on heating to afford initial quinonimines. Hydrolysis of the title compounds leads to formation of the corresponding quinones and N-arylsulfonylamidines.     

Microwave and quantum chemical study of propa-1,2-dienyl thiocyanate (H2C=C=CHSC triple bond N)

The microwave spectrum of propa-1,2-dienyl thiocyanate (H2C=C=CHSC triple bond N) has been investigated in the 24-40 and 50-80 GHz spectral regions. The spectrum of one conformer was assigned. This rotamer, which has a C-C-S-C dihedral angle of about 134 degrees from synperiplanar, is at least 2 kJ/mol more stable than any other form. Two vibrationally excited states assumed to belong to the first excited state of the C-S torsional vibration and to a low bending mode were assigned. Their frequencies were determined to be 62(20) and 155(30) cm-1, respectively. The microwave work has been augmented by ab initio calculations at the MP2/aug-cc-pVTZ and density functional theory calculations at the B3LYP/aug-cc-pVTZ level of theory. The B3LYP calculations are generally in better agreement with the observations than the MP2 calculations.