Ultrafast intramolecular charge transfer with strongly twisted aminobenzonitriles: 4-(di-tert-butylamino)benzonitrile and 3-(di-tert-butylamino)benzonitrile

The newly synthesized aminobenzonitriles with two bulky amino substituents 4-(di-tert-butylamino)benzonitrile (DTABN) and 3-(di-tert-butylamino)benzonitrile (mDTABN) have strongly twisted amino groups in the ground state. From X-ray crystal analysis it is found that the amino twist angle theta of mDTABN equals 86.5 degrees , whereas a twist angle of around 75 degrees is deduced for DTABN from the extinction coefficient of its lowest-energy absorption band in n-hexane. Because of the electronic decoupling between the amino and benzonitrile groups caused by these large twist angles, the absorption of DTABN and mDTABN is relatively weak below 40000 cm-1, with extinction coefficients around 25 times smaller than those of the planar 4-(dimethylamino)benzonitrile (DMABN). DTABN as well as mDTABN undergo efficient intramolecular charge transfer (ICT) in the singlet excited state, in nonpolar (n-hexane) as well as in polar (acetonitrile) solvents. Their fluorescence spectra consist of an ICT emission band, without evidence for locally excited (LE) fluorescence. The occurrence of efficient ICT with mDTABN is different from the findings with all other N,N-dialkylaminobenzonitriles in the literature, for which ICT only appears with the para-derivative. From solvatochromic measurements, an ICT dipole moment of 17 D is determined for DTABN as well as for mDTABN, similar to that of DMABN. The picosecond fluorescence decays of DTABN (time resolution 3 ps) are effectively single exponential. Their decay time is equal to the ICT lifetime tau'0(ICT), which increases with solvent polarity from 0.86 ns in n-hexane to 3.48 ns in MeCN at 25 degrees C. The femtosecond excited-state absorption (ESA) spectra of DTABN in n-hexane and MeCN at 22 degrees C show a decay of the LE and a corresponding rise of the ICT absorption. The ICT reaction time is 70 fs in n-hexane and 60 fs in MeCN. DTABN and mDTABN may have a strongly twisted ICT state, similar to that of 6-cyanobenzoquinuclidine but different from that of DMABN.     

Syntheses of 4-(2-hydroperoxy-2,2-diarylethyl)-3,5-dimethylpyrazoles, 4-(2-hydroxy-2,2-diarylethyl)-3,5-dimethylpyrazoles and the related compounds

The reactions of 1,1-disubstituted ethenes with 2,4-pentanedione in the presence of manganese(III) acetate and atmospheric oxygen yielded 4-acetyl-6,6-diaryl-3-methyl-1,2-dioxan-3-ols. The latter gave 4-(2-hydroperoxy-2,2-diarylemyl)-3,5-dimethylpyrazoles by the reaction with hydrazines in methanol-acetic acid (1:1 v/v) at 50° in 15-77% yields, or 4-(2-hydroxy-2,2-diarylethyl)-3,5-dimethylpyrazoles by the reaction with hydrazines in methanol in 2-78% yields. The acid-catalyzed reaction of 4-(2-hydroperoxy-2,2-diarylethyl)-3,5-dimethylpyrazoles yielded 4-(aroylmethyl)-3,5-dimethylpyrazoles (15-55%) and 4-(2,2-diarylethenyl)-3,5-dimethylpyrazoles (9-29%).     

Synthesis of 1-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-r-benzimidazoles

Reaction of 2,6-di-tert-butyl-1,4-benzoquinone with o-phenylendiamine gives 2,6-di-tert-butyl-1,4-benzoquinone-4-(N-o-aminophenyl)imine which reacts smoothly with heterocyclic, aromatic and aliphatic aldehydes to form (1-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-substituted benzimidazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 483–485, April, 1990.     

4-甲氧基-3-[3-(吗啉-4-基)丙氧基]苯甲腈的合成研究

以3-羟基-4-甲氧基苯甲醛为原料,在甲酸、甲酸钠、盐酸羟胺作用下,将醛基转化为氰基,在含有碳酸钾的DMF中,所得化合物与N-(3-氯丙基)吗啉反应得目标化合物,总收率为87.5%。产物结构由1HNMR表征。本方法具有操作简单、易于纯化、收率高等特点,为工业化生产提供实验基础。     

Antioxidant activity and superoxide anion radical interaction with 2-(ferrocenylmethylamino) benzonitrile and 3-(ferrocenylmethylamino) benzonitrile

Cyclic voltammetry was used to explore the interaction of (ferrocenylmethylamino) benzonitrile (FMAB) with superoxide anion radical (\({\text{O}}_{2}^{. - }\)), electrochemically generated by the reduction in commercial molecular oxygen in acetonitrile. The difference in the electrochemical behavior of \({\text{O}}_{2}^{. - }\) in the absence and presence of FMAB, including shifts in peak potential and decrease in anodic peak current, was successfully investigated for the determination of interaction parameters such as the binding constant, ratio of binding constants, binding free energy and mode of interaction. The anodic peak potential shifts and the magnitude of binding free energy ΔG suggest the electrostatic interaction of \({\text{O}}_{2}^{. - }\) with FMAB as the dominant mode, whereas the negative sign of ΔG indicates the spontaneity of the interaction. The antioxidant activity of FMAB derivatives was also evaluated using spectrophotometrical and electrochemical techniques. The spectrophotometrical assays were carried out using 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH), while the electrochemical assays were determined by measuring the oxidation peak current of \({\text{O}}_{2}^{. - }\). The activity was found to be highest for 3FMAB in both DPPH and \({\text{O}}_{2}^{. - }\) radicals scavenging methods (0.0183) and (0.0090 mg/mL), respectively, which is equal to half the antioxidant activity of standard antioxidant ascorbic acid (0.0117) and (0.0041 mg/mL).     

三氯化铁催化选择性合成普罗布考单丁二酸酯

研究了以三氯化铁为催化剂选择性合成普罗布考单丁二酸酯的反应.考察了催化剂、反应溶剂、碱、酰化剂及配料比对反应的影响.实验结果表明金属盐对反应的收率和单酰化反应的选择性有显著的影响,当以三氯化铁为催化剂,丁二酸酐为酰化剂,叔丁醇钠为碱,四氢呋喃为溶剂,普罗布考、叔丁醇钠、丁二酸酐及三氯化铁的摩尔比为1:4:5:0.17,...