Search results for "Intramolecular force"
showing 10 items of 599 documents
Borane reaction chemistry. Alkyne insertion reactions into boron-containing clusters. Products from the thermolysis of [6,9-(2-HC[triple bond]C-C5H4N…
2008
The stirring of [ortho-(HC[triple bond]C)-C(5)H(4)N] with [nido-B(10)H(14)] in benzene affords [6,9-{ortho-(HC[triple bond]C)-C(5)H(4)N}(2)-arachno-B(10)H(12)] 1 in 93% yield. In the solid state, 1 has an extended complex three-dimensional structure involving intramolecular dihydrogen bonding, which accounts for its low solubility. Thermolysis of 1 gives the known [1-(ortho-C(5)H(4)N)-1,2-closo-C(2)B(10)H(11)] 2 (13%), together with new [micro-5(N),6(C)-(NC(5)H(4)-ortho-CH(2))-nido-6-CB(9)H(10)] 3 (0.4%), [micro-7(C),8(N)-(NC(5)H(4)-ortho-CH(2))-nido-7-CB(10)H(11)] (0.4%) , 4 binuclear [endo-6'-(closo-1,2-C(2)B(10)H(10))-micro-(1(C),exo-6'(N))-(ortho-C(5)H(4)N)-micro-(exo-8'(C),exo-9'(N))-(…
Chiral Brønsted Acid-Catalyzed Asymmetric Allyl(propargyl)boration Reaction of ortho-Alkynyl Benzaldehydes: Synthetic Applications and Factors Govern…
2016
Chiral Bronsted acid-catalyzed allyl(propargyl)boration of ortho-alkynyl benzaldehydes gives rise to ω-alkynyl homoallylic(homopropargylic)alcohols that can be further transformed to complex molecular scaffolds via subsequent hydroalkoxylation, ring-closing enyne metathesis (RCEYM), or intramolecular Pauson–Khand reaction (PKR). Optimizations of each two-step transformation is reported. A strong dependence between enantioselectivities and the nature of the substitution at the alkynyl moiety is observed, showcasing that the triple bond is not merely a spectator in this transformation. Density functional theory (DFT) calculations (M06-2X/6-311+G(d,p)–IEFPCM//B3LYP/6-31G(d)) show that this dep…
Addition von Phosphor‐Nucleophilen an Benzothiet
1991
Addition Reactions of Phosphorus Nucleophiles to Benzothiete Trialkyl phosphites 4 add to the o-quinoid form 2 of benzothiete (1) to yield the phosphonates 6. An intermolecular migration of an alkyl group from oxygen to sulfur is the most important feature of this transformation. The rearrangement – related to the Arbuzov reaction – can be avoided in a two-step process by the subsequent action of PCl3 and alcohol; thus the phosphonates 10 are generated. Analogous to 2 6, dimethyl phenylphosphinate (11) furnishes 13. In contrast, the cyclic esters 14a–d form 2:1 adducts, namely the 12- to 15-membered heterocyclic compounds 17a – d. An intramolecular rearrangement in a 1:1 adduct is only obse…
C2-Symmetric Ferrocene-Bis(ureido)peptides : Synthesis, Conformation and Solid-State Structure
2009
The extension of peptide derivatives of ferrocene-1,1'-dicarboxylic acid by formal insertion of NH units between ferrocene and peptide strands results in ferrocene-bis(ureido)-peptides. Experimentally, alanine and dialanine methyl esters were attached to the 1- and 1'-position of 1,1'-diiso-cyanoferrocene to give the corresponding bis(ureido)peptide derivatives 3 and 4. The conformation of 3 has been determined in the solid state by X-ray crystallography. In solution the preferred conformation of 3 and 4 has been elucidated by NMR, IR and CD spectroscopy in concert with DFT calculations. The secondary structure of ferrocene―bis(ureido)peptides 3 and 4 is determined by double bifurcated intr…
Asymmetric Tandem Reactions: New Strategies and Applications
2013
Abstract The application of allylic sulphoxides and, particularly, the chiral amine reagent tert-butanesulphinamide has been extended to three different tandem processes. The condensation of (R)-(+)-allyl p-tolyl sulphoxide, fluorinated nitriles and alkyl propiolates led to a new family of enantiomerically pure fluorine-containing 1,4- dihydropyridines. A diastereoselective nucleophilic addition of fluorinated nucleophiles onto (R)-(tert-butanesulphinyl) imines, followed by an intramolecular aza-Michael reaction gave rise to either fluorinated isoindolines or 3-substituted indanones in a stereoselective manner.
ChemInform Abstract: Diastereoselective Intramolecular Additions of Allyl- and Propargylsilanes to Iminium Ions: Synthesis of Cyclic and Bicyclic Qua…
2010
Cyclization of the chiral imino lactones with allylic or propargylic groups required acidic conditions to afford spirocyclic (II) or (XII).
Selective access to either a doubly boron-doped tetrabenzopentacene or an oxadiborepin from the same precursor
2019
Depending on the solvent, a brominated arylborane gave the multiple helicene B2-TBPA (pyridine) or the oxadiborepin ODBE (THF) after intramolecular Yamamoto coupling.
Cooperative Effects in Aminothiols: Acid-Base Equilibria and the Molecular Structure of 2-(N, N-Dimethylaminomethyl)thiophenol
2008
Abstract 2-(N,N-Dimethylaminomethyl)thiophenol, (1, HL), is present as a non-zwitterionic aminothiol in the solid state, exhibiting an intramolecular S-H···N hydrogen bond. The S···N distances of the two independent molecules in the asymmetric unit are 2.929(10) and 3.050(10) Å. This structural feature is also present in an ab initio (MP2/6-31G*) optimized molecular structure. The investigation of the hydrogen bond by ab initio methods supports an n(N)-σ *(S-H) interaction as the reason for this bond type. On the basis of data from potentiometric acid-base titrations of a 0.01 M aqueous solution of [H2L]Cl with a 0.1 M aqueous solution of sodium hydroxide, values of 4.09±0.01 and 11.50±0.01…
Synthesis and structural studies on Ni(II) dithiocarbamates : Exploring intramolecular Ni···H-C interactions
2017
Abstract Five new Ni(II) dithiocarbamates with NiS4, NiS2PN and NiS2PCl coordination spheres, viz. [Ni(bupmbzdtc)2] (1), [Ni(bupmbzdtc)(PPh3)(NCS)] (2), [Ni(bupmbzdtc)(PPh3)Cl] (3), [Ni(4-dpmpzdtc)(PPh3)Cl] (4) and [Ni(pbbzbudtc)(PPh3)(NCS)] (5), where bupmbzdtc = N-butyl(p-methylbenzyl)dithiocarbamato anion, 4-dpmpzdtc = 4-(diphenylmethyl)piperazinecarbodithioato anion, pbbzbudtc = N-(p-bromobenzyl)butyl-dithiocarbamato anion and PPh3 = triphenylphosphine, were synthesized and characterized by UV, IR, NMR and single crystal X-ray diffraction methods. Spectral results suggest a square planar geometry around the Ni(II) metal center for all the synthesized complexes. Single crystal X-ray stru…
Synthesis, Structural, Magnetic and Thermal Characterization of {[Cu(bipy)] 2 (μ‐HP 2 O 7 )(μ‐Cl)}·H 2 O
2008
Copper(II) hydroxide reacts with 2,2′-bipyridine (bipy) and sodium pyrophosphate in a 2:2:1 stoichiometric ratio under ambient conditions at pH 1.6 in water. The resulting neutral dinuclear CuII complex features a bridging set containing bridging monoprotonated pyrophosphate and a monoatomic chloro bridge (making this the first pyrophosphate bridged coordination complex containing an alternate, additional halide bridge between the metal centers). Single-crystal X-ray diffraction studies revealed the complex to be {[Cu(bipy)]2(μ-HP2O7)(μ-Cl)}·H2O. The structure consists of a dimeric copper(II) system with each metal ion in a square pyramidal geometry. The asymmetric [Cu(bipy)]2+ units are br…