Xi:Irritant;7789-48-2Relevant articles and documents
Magnesium Halide-promoted Ring-opening Reaction of Cyclic Ether in the Presence of Phosphine Halide
Chang, Yu-Chang,Weng, Chia-Ming,Shaikh, Tanveer M.,Hong, Fung-E
, p. 703 - 711 (2015)
A new route to the direct preparation of H-phosphinate esters has been explored. The ring-opening reaction of cyclic ether (tetrahydrofuran or tetrahydropyrane) was carried out with magnesium halide in the presence of phosphine halide (PRCl2 or PCl3). The process is straightforward and all the reagents are relatively cheap and readily available. Magnesium halide-mediated THF ring-opening (SN2@C) and the subsequent SN2@P elementary reactions that giving rise to the intermediate of haloalkyl phosphinates have been discussed based on our experimental findings (Path I: SN2@C-+SN2@P). Another possible route, the direct SN2 between THF (nucleophile) and phosphine halide (electrophile) that followed by THF ring opening by halide dissociated from phosphine halide (Path II: SN2@P-+SN2@C), was also proposed. However, path II is the least likely reaction path because neutral THF is not a good nucleophile. H-phosphinate esters could be readily available in the subsequent hydrolysis process. Considering the ionic bond strength in magnesium halides and the nucleophilicity of halides dissociated from MgX2 in protic solvents like water, MgBr2 is recommended for ring-opening reactions of cyclic ethers.
Uniaxial orientational order-disorder transitions in diammine magnesium halides, Mg(ND3)2Cl2 and Mg (ND3)2Br2, investigated by neutron diffraction
Leineweber,Jacobs,Fischer,Boettger
, p. 487 - 499 (2001)
Neutron powder diffraction on Mg(ND3)2Cl2 and Mg(ND3)2Br2 revealed as a function of temperature uniaxial orientational order-disorder behavior of the ND3 groups. The crystal structures of both compounds are built up from chains of octahedra ∞1[Mg(NH3)2X4/2] with X=Cl and Br arranged in different ways relative to each other. At ambient temperatures (X=Cl) and 270 K (X=Br) the ND3 groups are disordered with respect to a rotation about the bond Mg-N. The D atom density is well described by a fourfold split position, each D site connecting an N with an X atom: Mg(ND3)2Cl2, Cmmm, a=8.1828(6) A, b=8.2007(6) A, c=3.7543(2) A, R(F2)Bragg=5.9%; Mg(ND3)2Br2, Pbam, a=5.9714(2) A, b=11.9175(3) A, c=3.98477(8) A, R(F2)Bragg=7.9%. In both cases the c axis corresponds to the direction of the chains ∞1[Mg(NH3)2X 4/2]. At low temperatures (8 K (X=Cl) and 1.5 K (X=Br)) both compounds are ordered with respect to the ND3 groups: They are arranged antiferroelectrically on either side of the chains ∞1[Mg(NH3)2X 4/2]. The symmetry is lowered compared to the situation at ambient temperatures and 270 K respectively, which involves in both cases a doubling of the orthorhombic c axis: Mg(ND3)2Cl2, Ibmm, a=8.1319(3) A, b=8.1338(3) A, c=7.4410(2) A, R(F2)Bragg=5.9%; Mg(ND3)2Br2, Pnam, a=5.92837(8) A, b=11.8448(2) A, c=7.9117(1) A, R(F2)Bragg=5.0%. Detailed evaluation of neutron diffraction data of Mg(ND3)2Cl2 as a function of temperature (50 Kt ≈ 135K.
Chemistry of c-trimethylsilyl-substituted heterocarboranes. 23. synthetic, spectroscopic, and structural investigation on half- and full-sandwich Magnesacarboranes of 2,3- and 2,4-C2B4 carborane ligands
Hosmane, Narayan S.,Zhu, Dunming,McDonald, James E.,Zhang, Hongming,Maguire, John A.,Gray, Thomas G.,Helfert, Sarah C.
, p. 1426 - 1437 (1998)
The reaction of nido-1-Na(L)n-2-(SiMe3)-3-(R)-2,3-C2B 4H5 (n = 2, L = THF, R = SiMe3; n = 1, L = TMEDA, R = SiMe3 or Me) or closo-exo-5,6-[(μ-H)2Li(L)n]-1-Li(L) n-2,4-(SiMe3)2-2,4-C2B 4H4 (n = 2, L = THF; n = 1, L = TMEDA) with various magnesium reagents produced a number of different magnesacarboranes. The product of a 1:1 molar ratio reaction of the 2,3-C2B4 monosodium compound (R = SiMe3 and L = TMEDA) with MeMgBr was the half-sandwich magnesacarborane closo-1-Mg(TMEDA)-2,3-(SiMe3)2-2,3-C2B 4H4 (I), while when R = Me, the same reaction conditions gave the novel full-exo-sandwich complex commoexo-4,4′,5,5′-Mg(TMEDA)[2-(SiMe3)-3-(Me)-2,3-C 2B4H5]2 (II). The full-endo-sandwich magnesacarboranes [Na(THF)2]2[commo-1,1′-Mg{2,3-(SiMe 3)2-2,3-C2B4H4} 2] (IV) and [Na-(TMEDA)]2[commo-1,1′-Mg{2,3-(SiMe3) 2-2,3-C2B4H4}2] (V) were the exclusive products when the appropriate monosodium compound reacted with Mg(Bu)2 in 2:1 molar ratios. Reaction of closo-exo-5,6-[(μ-H)2Li(TMEDA)]-1-Li(TMEDA)-2,4-(SiMe 3)2-2,4-C2B4H4 with MgBr2 in a 1:1 molar ratio produced closo-1-Mg(TMEDA)-2,4-(SiMe3)2-2,4-C2B 4H4 (III), while a 2:1 molar ratio gave [Li(TMEDA)2]2[commo-1,1′-Mg{2,4-(SiMe 3)2-2,4-C2B4H4} 2] (VI). The yields ranged from 73% for III to 94% for II. On the other hand, the 1:1 molar ratio reaction of the THF-solvated 2,4-C2B4 disodium compound with MeMgBr, followed by the addition of 1 equiv of the THF-solvated monosodium compound of the 2,3-C2B4 carborane did not give the expected mixed-ligand complex but produced a 50:50 mixture of IV and [Li(THF)2]2[commo-1,1′-Mg-{2,4-(SiMe 3)2-2,4-C2B4H4} 2] (VII) in nearly quantitative yields. The magnesacarboranes were characterized by their infrared spectra, chemical analysis, H1, 11B, and 13C NMR spectra, and, in the case of VII, by its 7Li NMR spectrum. Compounds I, II, and IV were further characterized by single-crystal X-ray analysis. Compound I crystallizes as a dimer in which a Mg occupies the apical position above the pentagonal face of one carborane and is bonded to the unique boron of the other carborane in the dimer through a Mg-H-B bridge. The structure of II is one in which a TMEDA-solvated Mg is exo-polyhedrally bonded to two 2,3-C2B4 monoanionic ligands through a pair of Mg-H-B bridges, while in IV, the two carborane dianions are η5-bonded to a Mg in a more conventional endo-sandwich complex. The reactions with MeMgBr are thought to proceed through the formation of a methylmag-nesacarborane intermediate which undergoes further reaction to give the final products. The 11B NMR spectra of I-VII were analyzed with the aid of ab initio GIAO molecular orbital calculations.
Aziridine Ring Opening as Regio-and Stereoselective Access to C-Glycosyl-Aminoethyl Sulfide Derivatives
Le?niak, Stanis?aw,Malinowska, Martyna,Tracz, Aleksandra,Zawisza, Anna
, (2022/03/23)
A short synthetic route to stereoselective access to C-glycosyl-aminoethyl sulfide derivatives has been developed through the reaction of tributhyltin derivatives of glycals with aziridinecarboaldehyde and the regioselective ring opening of a chiral aziridine with thiophenol. The absolute configurations of the resulting diastereoisomers were determined by 1H NMR spectroscopy.
Copper-Catalyzed Regio- and Enantioselective Addition of Silicon Grignard Reagents to Alkenes Activated by Azaaryl Groups
Mao, Wenbin,Xue, Weichao,Irran, Elisabeth,Oestreich, Martin
supporting information, p. 10723 - 10726 (2019/07/04)
A new application of silicon Grignard reagents in C(sp3)?Si bond formation is reported. With the aid of BF3?OEt2, these silicon nucleophiles add across alkenes activated by various azaaryl groups under copper catalysis. An enantioselective version employing benzoxazole-activated alkenes as substrates and a CuI-josiphos complex as catalyst has been developed, forming the C(sp3)?Si bond with good to high enantiomeric ratios (up to 97:3). The method expands the toolbox for “conjugate addition” type C(sp3)?Si bond formation.
