Novel tetraalkyltetraboranes of the type B4R4, B4H2R4 and B4H4R4
摘要:
The reduction of RBHal(2) (Hal = F, Cl, Br) with Na/K alloy gives the tetraboranes B4R4, B4H2R4 or their mixtures, depending on temperature, reaction time and solvent. We describe here (B4Bu4)-Bu-t, B-4((CH2Bu)-Bu-t)(4) (B4H2Bu4)-Bu-t, B4H2((CH2Bu)-Bu-t)(4) and B4H2(CMe2Et)(4). (B4Bu2)-Bu-t((CH2Bu)-Bu-t)(2) is formed by reducing the diborane Cl-B(Bu-t)-B((CH2Bu)-Bu-t)-Cl with Li. The conversion of (B4H2Bu4)-Bu-t into (B4H4Bu4)-Bu-t proceeds in three steps: (i) reduction (-->[(B4H2Bu4)-Bu-t](2-)); (ii)first protonation (-->[(B4H3Bu4)-Bu-t](-)), and (iii) second protonation (-->(B4H4Bu4)-Bu-t). The hypercloso-species B4R4 have: tetrahedral structures. The two opposite edges of a B-4 tetrahedron of the closo-B4H2R4 are bridged by H atoms (D-2d). The nido-species have a bicyclobutane-type B-4 skeleton; three of the four outside edges are bridged by H atoms; two terminal ligands are bound to one of the B atoms: H in exo- and Bu-t in endo-position (C-1). Structural evidence is based on low-temperature NMR spectra, ab initio geometries, and IGLO(DZ) calculations of the B-11 NMR shifts. Dynamical behavior of bridging H atoms is indicated by the NMR spectra at higher temperature. (C) 1999 Elsevier Science S.A. Pill rights reserved.
[EN] MACROCYCLIC BROAD SPECTRUM ANTIBIOTICS<br/>[FR] ANTIBIOTIQUES MACROCYCLIQUES À LARGE SPECTRE
申请人:RQX PHARMACEUTICALS INC
公开号:WO2018149419A1
公开(公告)日:2018-08-23
Provided herein are antibacterial compounds, wherein the compounds in some embodiments have broad spectrum bioactivity. In various embodiments, the compounds act by inhibition of bacterial type 1 signal peptidase (SpsB), an essential protein in bacteria. Pharmaceutical compositions and methods for treatment using the compounds described herein are also provided.
A three-component reaction of potassium alkyltrifluoroborates, the sulfurdioxide surrogate of DABCO·(SO2)2, and alkenes under photocatalysis in the presence of visible light is developed. This reaction works efficiently at room temperature with the insertion of sulfurdioxide under mild conditions, affording diverse sulfones in good to excellent yields. The alkyl radical and alkylsulfonyl radical
A photoinduced reaction of potassium alkyltrifluoroborates, sulfur dioxide, and para-quinone methides under visible light irradiation at room temperature is developed, giving rise to diarylmethyl alkylsulfones in moderate to good yields. This reaction works well under photocatalysis with a broad substrate scope by using DABCO·(SO2)2 as the source of sulfur dioxide. Mechanistic study shows that this
Saturated oxygen and nitrogen heterocycles <i>via</i> oxidative coupling of alkyltrifluoroborates with alkenols, alkenoic acids and protected alkenylamines
作者:Jonathan M. Shikora、Chanchamnan Um、Zainab M. Khoder、Sherry R. Chemler
DOI:10.1039/c9sc02835h
日期:——
Saturated heterocycles are important components of many bioactive compounds. The method disclosed herein enables a general route to a range of 5-, 6- and 7-membered oxygen and nitrogenheterocycles by coupling potassium alkyltrifluoroborates with heteroatom-tethered alkenes, predominantly styrenes, undercopper-catalyzedconditions, in the presence of MnO2. The method was applied to the synthesis of
Synthesis of α-Fluoro-α-amino Acid Derivatives via Photoredox-Catalyzed Carbofluorination
作者:Jaehoon Sim、Mark W. Campbell、Gary A. Molander
DOI:10.1021/acscatal.8b04284
日期:2019.2.1
A mild, metal-free, regioselective carbofluorination of dehydroalaninederivatives has been developed. Alkyl radicals resulting from visible-light photoredox catalysis engage in a radical conjugate addition to dehydroalanine, with subsequent fluorination of the newly generated radical to afford an α-fluoro-α-amino acid. By using a highly oxidizing organic photocatalyst, this process incorporates non-stabilized