Nucleophilic addition of 2-hydroxyquinoxaline to acetylenes

Vinylation of 2-hydroxyquinoxaline affords either 2-vinyloxyquinoxaline or 1-vinyl-2-quinoxalone depending on the reaction conditions. The reactions of 2-hydroxyquinoxaline with 3-phenylprop-2-ynonitrile or 4-hydroxyalk-2-ynonitriles yield 3-phenyl-3-(quinoxalyl-2-oxy)prop-2-enonitrile or 4-hydroxy-3-(quinoxalyl-2-oxy)alk-2-enonitriles, respectively. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 738–741, April, 2000.     

阳极微分脉冲伏安法测定3,4-二氢-2-羟基喹噁啉

3,4-二氢-2-羟基喹(?)啉(简称二氢喹(?)啉)是合成新型有机磷农药及一些喹(?)啉磺胺类药物的中间体.本文根据二氢喹(?)啉可被氧化成2-羟基喹(?)啉的性质,进行了阳极微分脉冲伏安法研究.结果表明,以玻碳电极为工作电极,在甲醇和Britton-Robinson混合液中,二氢喹(?)啉有良好的微分脉冲伏安峰.用此法测定了2-羟基喹(?)啉中二氢喹(?)啉的含量.经循环伏安法验证,电极反应为不可逆反应.     

Reinvestigation of the stereochemistry of kulokekahilide-2

An attempt to carry out a total synthesis of kulokekahilide-2 (1) by macrolactonization of a seco acid prepared from a suitably protected hexapeptide and a dioxy acid moiety unexpectedly resulted in the formation of the 43-epimer (1a) of the cytotoxic depsipeptide, for which structure 1b has previously been proposed. A second attempt involving macrolactamization of the corresponding amino acid gave the target product, 1b, but the spectral data of the product did not match those of natural 1. Furthermore, neither 1a nor 1b showed any cytotoxicity, from which it is concluded that the structure of natural 1 is incorrect and should be re-examined.     

Reinvestigation of the rearrangement of 2-acetylbenzofuran oxime tosylate

The acetal, resulting from the rearrangement of anti-2-acetylbenzofuran oxime tosylate (I) was proved to be a mixture of trans- (IX) and cis- (X) 2,3-dihydro-2-acetyl-2,3-dimethoxybenzofuran. The structure of these isomers as well as that of their oximes XI and XII was elucidated by ir, nmr, and mass spectral investigation and by the ir and nmr spectra of the benzoyl (XIII and XIV) and acetyl (XV and XVI) derivatives of the oximes. A new reaction mechanism concerning the rearrangement process is discussed.     

Reinvestigation of the synthesis of 5-arylamino-2-picolines

Reaction of 5-bromo- or 3-bromo-2-methylpyridine with o-nitroaniline gave the corresponding N-[2-methyl-5(or 3)pyridyl]-o-nitroanilines. Reduction to the corresponding amino derivatives and ring closure to 1-[2-methyl-5(or 3)pyridyl]benzotriazole allowed the structures to be confirmed and an earlier literature report to be corrected. Displacement of bromide by anthranilic acid from 5-bromo-2-methylpyridine and decarboxylation gave N-(2-methyl-5-pyridyl)aniline.     

Reinvestigation of the condensation of 2-hydrazinobenzothiazole with ethyl acetoacetate

The reaction of 2-hydrazinobenzothiazole (1) with ethyl acetoacetate has twice been reported to yield a fused triazepinobenzothiazolone, namely, 3-methyl[1,2,4]triazepino[3,4-b]benzothiazol-5(4H)-one (4). We have repeated this work and reassigned the reaction product as 2-(2-benzothiazolyl)-1,2-dihydro-5-methyl-3H-pyrazol-3-one (5) on the basis of X-ray crystallography.     

The Reaction of Diethanolamine with 2-Chloronitrobenzene-A Reinvestigation

In a report on the reaction of 2-chloronitrobenzene (1) with diethanolamine (2), Meltsner et al ¹ claim that the expected S_NAr product, N-(2-nitrophenyl)diethanolamine (3), is not formed; rather that the products are 2,2′-dichloroazobenzene (4), 2-nitrophenol (5), 2-chloroaniline (6) and 4-(2-aminophenyl)morpholine (7). Similar products in which the nitro function is reduced are also reported² for the corresponding reaction with ethanolamine. In this laboratory, in an attempted preparation of 2,2′-dichloroazobenzene (4) for reference purposes in photochemical studies on the antineoplastic agent 5-(3-azido-4-chlorophenyl)-6-ethyl-pyrimidin-2,4-diamine³, the expected S_NAr product (3) was obtained along with other products.     

Reinvestigation of the GaMn structure and theoretical studies of its electronic and magnetic properties

The crystal structure of the binary gallide compound GaMn is reinvestigated using X-ray diffraction. The structure is quite different from that proposed previously. Although GaMn is reported to crystallize with the Al₈Cr₅ structure type, space group R3m, we found that the centrosymmetric space group , with a=12.605(2) Å and c=8.0424(11) Å, was more accurate. Moreover, the atomic positions and the atomic displacement parameters, which are missing in the previous study, are now refined. Thereafter, band structure calculations have been performed using the TB-LMTO-ASA method to understand the electronic and magnetic properties of this compound. Analyses from the band structure, the density of states and the magnetic moments obtained using spin-polarized calculations show the stability of two different magnetic models relative to the nonmagnetic one.     

Reinvestigation of prototropic photochromism: 3-benzoyl-2-benzylchromones

The synthesis of a series of new nine 3-benzoyl-2-benzylchromones is developed through a classical and an optimized Kostanecki-Robinson method involving an o-hydroxyphenyl-β-diketone and an acid anhydride. The different spectrokinetic studies carried out in solution and in polymer matrixes have highlighted the main structure/photochromic parameters relationships and the influence of the medium on the photochromic properties.     

Structure and products of oxidative amination of 6-hydroxyquinoxaline

3-Morpholino-6-methoxy-5,8-quinoxalinequinone was synthesized by a method which excludes the formation of isomers, and was used for proving the structure of products of the oxidative amination of 6-hydroxyquinoxaline as 2,8-bis(dialkylamino)-5,6-quinoxalinequinones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, 1671–1672, December, 1985.