o‐Benzenedicarbaldehyde (systematic name: benzene‐1,2‐dicarbaldehyde), C8H6O2, exhibits a weak intramolecular hydrogen bond between an aldehyde H atom and the O atom of the adjacent aldehyde group, with a C?O distance of 2.852 (2) Å. m‐Benzenedicarbaldehyde (systematic name: benzene‐1,3‐dicarbaldehyde), C8H6O2, occurs as two different isomorphs. In all three crystals, there are intermolecular C—H?O contacts involving both aldehyde and ring H atoms. 相似文献
The structures of o‐chlorobenzonitrile, C7H4ClN, (I), and o‐bromobenzonitrile, C7H4BrN, (II), have similar packing arrangements, even though Z′ = 4 in (I) and Z′ = 1 in (II). Both structures involve X⋯N interactions, as well as weak C—H⋯X and C—H⋯N hydrogen bonds. The four crystallographically independent molecules in (I) are related by pseudosymmetry. 相似文献
A nickel‐catalyzed arylation at the carbon center of o‐carborane cages has been developed, thus leading to the preparation of a series of 1‐aryl‐o‐carboranes and 1,2‐diaryl‐o‐carboranes in high yields upon isolation. This method represents the first example of transition metal catalyzed C,C′‐diarylation by cross‐coupling reactions of o‐carboranyl with aryl iodides. 相似文献
In the crystal structure of the title compound, 2C22H24P+·I82−, the I82− anion is located on a crystallographic inversion centre and consists of two tri‐iodide anions linked by di‐iodine at angles of 89.92 (4)° to form a planar `Z'‐shaped dianion. The octaiodides are linked via long‐range interactions [3.877 (11) Å] into infinite polyiodide ribbons. This is the first example of a structure containing an [(o‐tolyl)3PMe]+ cation, and the CMe—P—C—CMe torsion angles of −54.0 (11), −51.3 (11) and −48.2 (11)° indicate that the configuration is exo3. 相似文献
The synthesis and properties of biphenyl‐ and p‐terphenyl‐fused o‐carboranes are described. Aryl rings in the biphenyl and p‐terphenyl skeletons are highly coplanar because of the presence of the o‐carborane unit. o‐Carborane exhibits an electron‐withdrawing character via the inductive effect, resulting in a decrease in both the HOMO and LUMO levels of oligophenyls without causing electronic perturbation. 相似文献
1,3‐Dehydro‐o‐carborane is a useful synthon for selective cage boron functionalization of o‐carboranes. It reacts readily with alkenes or alkynes to give a variety of cage B(3)‐alkenyl/allenyl o‐carboranes by ene reactions in very high yields and excellent regioselectivity. This can be ascribed to the highly polarized cage C?B multiple bond, which lowers the activation barriers of the ene reaction. 相似文献
Photolysis of ester 1 in argon‐saturated methanol and acetonitrile does not produce any product, whereas irradiation of 1 in oxygen‐saturated methanol yields peroxide 2 . Laser flash photolysis studies demonstrate that 1 undergoes intramolecular H atom abstraction to form biradical 3 (λ max ~ 340 nm), which intersystem crosses to form photoenols Z ‐ 4 and E ‐ 4 (λ max ~ 380 nm). Photoenols 4 decay by regenerating ester 1 . With the aid of density functional theory calculations, it was concluded the photoenol E ‐ 4 does not undergo spontaneous lactonization or electrocyclic ring closure because the transition state barriers for these reactions are too large to compete with reketonization of E ‐ 4 to form 1 . 相似文献
Stepwise demethylation of fluorescent 6,7‐dimethoxy‐3‐trifluoromethylcarbostyrils 5 leads to 6‐hydroxy derivatives 6 and 6,7‐dihydroxyderivative 7 . Phenolate formation shifts excitation and emission maxima from 370 and 430 nm to 430 and 480 nm for the anion of 6 and as far as 500 and 580 nm for the dianion of 7 . Dependence of fluorescence quantum yield on media and polar structure, varying from 0.02 to 0.51, is discussed. O‐Alkylation of 6 with alkyl bromoacetate yields esters of type 8 in good yield. Reactive succinimidoyl (OSu) esters of type 11 were prepared after saponification to acids 9 . With amino acids or their esters, peptides and aminoglucose, linking to labeled derivatives 13 or 15 could be achieved under mild conditions in slightly basic aqueous media. 相似文献
The new mono‐ and binuclear semiquinonato dimethylthallium complexes (Q‐TTF‐SQ)TlMe2 ( 1 ) and Me2Tl(SQ‐TTF‐SQ)TlMe2 ( 2 ) based on di‐o‐quinone with tetrathiafulvalene (TTF) bridge, 4,4′,7,7′‐tetra‐tert‐butyl‐2,2′‐bis‐1,3‐benzodithiol‐5,5′,6,6′‐tetraone Q‐TTF‐Q, were synthesized by the reaction between corresponding mono‐ and di‐sodium semiquinonates (Q‐TTF‐SQ)Na and Na(SQ‐TTF‐SQ)Na and one or two equivalents of Me2TlCl, respectively. The same products could be obtained by the interaction of Q‐TTF‐Q with one or two equivalents of Me3Tl. Complexes 1 and 2 were characterized by IR and electronic absorption spectroscopy, EPR, and magnetic measurements. The molecular structures of 1 and 2 were determined by single‐crystal X‐ray diffraction. It was found that mono‐semiquinonato derivative 1 partially disproportionates into Q‐TTF‐Q and binuclear complex 2 in THF solution. According to variable temperature magnetic susceptibility measurements and EPR data, compound 1 reveals paramagnetic behavior with an S = 1/2 state in the range 50–300 K, whereas compound 2 has an S = 0 ground state as the consequence of antiferromagnetic coupling between semiquinonato moieties realized through the TTF‐bridge. 相似文献
The synthesis of novel luminescent polymer containing p‐phenylene‐ethynylene and 9,12‐linked o‐carborane units alternately in the main chain is reported. The obtained polymer exhibits intense blue photoluminescence, providing the first insights into the optical properties of a 9,12‐disubstituted o‐carborane dye. π‐Conjugated substituent at 9 and/or 12‐positions in o‐carborane is electrically independent, and both the HOMO and the LUMO levels slightly increase, whereas LUMO of the π‐conjugated substituent at 1 and/or 2‐positions in o‐carborane decrease. Thus, it is deduced that polymers consisting of the 9,12‐linked o‐carborane unit are able to be applied as light‐emitting materials.
Dimethyl acetylenedicarboxylate (DMAD) is a very important and useful reagent for the preparation of dimethyl heterocyclic‐o‐dicarboxylates, which are key intermediates in the synthesis of fused pyridazine derivatives. The synthesis of thiopyranes by the Diels‐Alder reaction of dithiocarboxylate derivatives, synthesis of various cyclazines by [2 + 8] cycloaddition reactions, and synthesis of dimethyl pyrazolo[3,4‐b]pyridine‐5,6‐dicarboxylates and polycyclic heterocycles containing the 1,6‐naphthyridine ring system by the reaction of o‐aminonitrile compounds with DMAD are described here. 相似文献
Sealed tube reactions of the naphthosultine 8 with a series of electron‐deficient dienophiles (fumaronitrile, N‐phenylmaleimide, dimethyl fumarate, and dimethyl acetylenedicarboxylate) in toluene at 180 °C gave corresponding 1:1 cycloadducts 11–14 in various amounts along with rearranged naphthosulfolene 7 in 67–95% yields. The reaction of 1,2,4,5‐tetra(bromomethyl)benzene with Rongalite (sodium form aldehyde sulfoxylate) and tetrabutylammonium bromide in DMF gave benzodisultines 17 and 18 in a combined yield of 56%. Sealed tube reactions of benzodisultines 17 and 18 with a series of dienophiles in xylene at 200 °C gave corresponding 1:1 and 1:2 cycloadducts 20–27 . The results suggested that thermal extrusion of sulfurdioxide from these sultines led to either o‐naphthoquinodimethane 6 (from 8 ) or bis‐o‐quinodimethane 19 (from 17 and 18 ); sub sequent trapping of these reactive intermediates by dienophiles and SO2 gave various 1:1 and 1:2 Diels‐Alder ad ducts in modest to excellent yields. 相似文献