Elemental fluorine. Part 24.[1]: Fluorination of ethers by fluorine and Selectfluor

Reactions of dialkyl ethers with either fluorine or Selectfluor™ led to the formation of unusual difluorinated polyether products in modest yields. A mechanism involving initial fluorination of the site adjacent to ether oxygen followed by elimination of hydrogen fluoride, reaction of the generated enol system with a further equivalent of fluorinating agent giving an oxonium system which reacts with water during aqueous work-up to lead eventually to the products observed, is suggested.     

Reactions of 1-Substituted Benzo[4,5]imidazo[1,2-a]pyridines

Bromination of 1-oxo(imino, amino)benzo[4,5]imidazo[1,2-a]pyridines gave the corresponding 2-bromo derivatives. Acylation using the Vilsmeier complex in acetic anhydride gave the N-formyl and N-acetyl derivatives. The reaction of the amine with the Vilsmeier complex, acetyl acetone, ethyl acetoacetate, and 2,5-dimethoxytetrahydrofuran occurs at the amino group.     

The reactivity of 1,1-diamino-2,2-dinitroethene (FOX-7)

The reactivity of 1,1-diamino-2,2-dinitroethene (DADNE) or FOX-7 was studied. Various reactions like cycloadditions, nitration, halogenation and acylation were performed in order to evaluate the reactivity of the C-C double bond and the amino moieties. Several products were isolated and two of them were characterised by X-ray analysis. Two reactive sites were identified. The chemical behaviour of DADNE is also discussed.     

Metal-free electrophilic fluorination of alkyl trifluoroborates and boronic acids

Secondary alkyl trifluoroborates undergo facile electrophilic fluorination under mild conditions to afford the corresponding benzylic fluorinated adducts in excellent yield.     

Preparation of halo enol phostones by reaction of acetylenic phosphonate monoesters with (bis-collidine)halo hexafluorophosphate

Reaction of non-conjugated acetylenic phosphonate monoesters with (bis-collidine) bromo and iodo hexafluorophosphates was found to lead to the formation of halo enol phostones. Depending on the size of the heterocyclic compounds formed (6-8-membered compounds), endo or a mixture of endo and exo cyclization products were obtained.     

H_3PO_4/Zr(OH)_4高效促进NBS对取代烷基苯的亲电溴代

使用固体酸H3PO4/Zr(OH)4催化NBS对取代烷基苯进行苯环溴代反应.根据不同取代烷基苯的反应活性,在乙腈中,高产率(79%～96%)地得到了相应的苯环单溴代产物,同时反应体系中无苄位溴代的副产物生成.在反应过程中,固体酸催化剂可以重复使用多次.     

Electrophilic glycosidation employing 3,5-O-(di-tert-butylsilylene)-erythro-furanoid glycal leads to exclusive formation of the β-anomer: synthesis of 2′-deoxynucleosides and its 1′-branched analogues

Stereoselectivity in N-iodosuccimide (NIS)-mediated electrophilic glycosidation was examined by employing 2,4-bis-O-(trimethylsilyl)thymine and three different silyl-protected erythro-furanoid glycals 12, 16, and 18. As a result, it was found that 3,5-O-(di-t-butylsilylene)-protected 18 gave only the β-anomer (21). The remarkable stereoselectivity observed by employing 18 is discussed on the basis of its X-ray crystallographic analysis. 1-Substituted glycals gave the corresponding β-anomer, again exclusively, to provide access to 1′-branched 2′-deoxynucleosides.     

Synthesis of substituted quinolines by the electrophilic cyclization of n-(2-alkynyl)anilines

A wide variety of substituted quinolines are readily synthesized under mild reaction conditions by the 6-endo-dig electrophilic cyclization of N-(2-alkynyl)anilines by ICl, I₂, Br₂, PhSeBr, and p-O₂NC₆H₄SCl. The reaction affords 3-halogen-, selenium- and sulfur-containing quinolines in moderate to good yields in the presence of various functional groups. Analogous quinolines bearing a hydrogen in the 3-position have been synthesized by the Hg(OTf)₂-catalyzed ring closure of these same alkynylanilines.