基于苯并硫氮杂卓的亚胺、烯胺在质子溶剂中的稳定性及其互变异构

用核磁共振法研究了亚胺型杂卓1和烯胺型杂卓2在不同质子溶剂—甲醇、乙醇、叔丁醇、乙酸及CF3CO2D的DMSO-d6溶液中的稳定性及互变异构.结果表明,烯胺型杂卓2在上述溶剂中稳定,亚胺型杂卓1在酸性较弱的质子溶剂中(乙醇、叔丁醇)及较低的温度下(≤30℃)基本稳定,在酸性较强的质子溶剂中(甲醇、乙酸、CF3CO2D的DMSO-d6溶液)向烯胺转化,而且随着溶剂酸性的增强、温度的升高以及反应物与溶剂接触时间的延长,亚胺向烯胺的转化进一步加强.本文还以1a和1b为例,研究了在乙酸溶液中亚胺型杂卓向烯胺型杂卓转化的热力学和动力学特征.研究表明,在283~333 K范围内,该转化的焓变(△H)和熵变(△S)均大于零,吉布斯自由能变(△G)小于零,因此其是吸热、自发及熵增加的过程,该过程可用二级动力学方程来描述,质子对亚胺向烯胺的转化起催化作用.     

Synthesis of Some Heterocyclic Compounds from Enamines of 3-Acetylfuran-2(5 H)-ones

The interaction of different 3-acetylfuran-2(5H)-ones (1, 4) with dimethylformamide dimethyl acetal (DMF/DMA) has been investigated, and the condensed furopyridine system 3 was obtained. By means of interaction of compounds 4 and DMF/DMA via the 3-acetylfuran-2(5H)-one enamines, the heterocyclic substituted furanones are obtained. The condensation of 3-acetyl-4,5,5-trimethylfuran-2(5H)-one (1a) with veratraldehyde was realized. Through the interaction of 1a with malononitrile and further intramolecular condensation of the product, 6-amino-dihydroisobenzofuran-5-carbonitrile was also synthesized.     

Attempts to Rationalize the Chemical Reactivity of the 1–3 Dipolar Species Obtained when a Phosphite Reacts with Activated Ethylenic or Acetylenic Ketones or Esters

Abstract

- Addition of trivalent phosphorus compounds with α, β ethylenic ketones and esters leads to examples of prototropy or cyclisation or rearrangement with ring expansion from 5 to 7 atoms.

When trivalent phosphorus compounds react with acetylenic ketones and esters, the 1, 3 dipolar species can be trapped with an electrophilic reagent (aldehydes or the original acetylenic compound) or a protic reagent (alcohol, acid, amide, phenol, etc…) Ylides, phosphoranes, spirophos-phoranes and phospholes can be obtained.     

Reaction of N-acetylimidazole with enamines

N-Acetylimidazole is a commonly used acylating reagent. When it is allowed to react with several typical enamines, amides are produced rather than the expected acylated enamines.     

New approach to CF3-containing polysubstituted anilines: reaction of β-trifluoroacetylvinyl ethers with enamines

The reaction of β-trifluoroacetylvinyl ethers with ‘push-pull’ enamines having a methyl group at the α-position was investigated. As a result, a set of CF₃-containing dialkyl anilines and their covalent hydrates were obtained. A possible reaction mechanism and the stability of the covalent hydrates obtained are discussed.     

Organomediated Enantioselective 18F Fluorination for PET Applications

The first organomediated asymmetric ¹⁸F fluorination has been accomplished using a chiral imidazolidinone and [¹⁸F]N‐fluorobenzenesulfonimide. The method provides access to enantioenriched ¹⁸F‐labeled α‐fluoroaldehydes (>90 % ee), which are versatile chiral ¹⁸F synthons for the synthesis of radiotracers. The utility of this process is demonstrated with the synthesis of the PET (positron emission tomography) tracer (2S,4S)‐4‐[¹⁸F]fluoroglutamic acid.     

Purins,pyrimidines, and related condensed systems. 22. Synthesis and heterocyclization of 7-alkynyl- and 6,7-dialkynyllumazines

The reaction of 6,7-dichloro-1,3-dimethyllumazine with terminal alkynes under Sonogashira conditions gave 7-alkynyl-6-chloro- and 6,7-dialkynyl-1,3-dimethyllumazines. It was found that the alkynyllumazines readily add primary and secondary alkylamines at the 7-alkynyl group to form stable enamines, hydrolysis of which gives 7-(-hydroxyvinyl)lumazines. The heterocyclization of 7-(-aminovinyl)- and 7-(-hydroxyvinyl)lumazines has been carried out to give pyrrolo-, pyrido-, furo-, and pyranopteridines.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 140–152, January, 2005.