The molecular structure of 4-tert-butylpyrazoles in the solid state and in solution: an X-ray, NMR and calorimetric study of the buttressing effect of a 4-tert-butyl substituent

2001 ◽  
Vol 25 (6) ◽  
pp. 819-823 ◽  
Author(s):  
Swiatoslaw Trofimenko ◽  
Arnold L. Rheingold ◽  
Louise M. Liable-Sands ◽  
Rosa María Claramunt ◽  
Concepción López ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Solid State ◽  
Calorimetric Study ◽  
X Ray ◽  
Tert Butyl

Crystal structure – reactivity correlations in the solid state photochemistry of N-(tert-butyl)succinimide

1994 ◽  
Vol 72 (9) ◽  
pp. 1952-1960 ◽  
Author(s):  
Tai Y. Fu ◽  
John R. Scheffer ◽  
James Trotter
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Solid State ◽  
Crystalline State ◽  
Crystal And Molecular Structure ◽  
Carbonyl Oxygen ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Tert Butyl ◽  
Close Contacts

In order to provide experimental evidence on the stereoelectronic requirements for intramolecular hydrogen atom abstraction by carbonyl oxygen, N-(tert-butyl)succinimide, 1, was investigated by the crystal structure – reactivity correlation method. In this method, the success or failure of a given reaction in the crystalline state is correlated with the geometric parameters associated with the process as determined by X-ray crystallography. In the case of N-(tert-butyl)succinimide, the crystal and molecular structure shows that the molecule adopts a conformation in which there are very close contacts (d = 2.17–2.24 Å) between the carbonyl oxygen atoms and certain γ-hydrogen atoms on the tert-butyl group. In accord with these close contacts, ultraviolet irradiation of N-(tert-butyl)succinimide in the crystalline state leads to transfer of one of the γ-hydrogen atoms from carbon to oxygen. This produces a 1,4-biradical which closes to form a cyclobutanol, and the cyclobutanol undergoes ring opening to afford the final stable product, tetrahydro-1H-azepine-2,5-dione, 2. The crystal and molecular structure of photoproduct 2 is also reported. In contrast to many solid state transformations, there was no discernable melting of the crystals during reaction, and complete conversions of 1 into 2 could be achieved. The isolated chemical yield of photoproduct 2 from the solid state reaction (79%) is in fact considerably higher than that reported by Kanaoka and Hatanaka for the corresponding solution phase process (49%). This permitted the solid state reaction to be followed to 100% conversion by X-ray powder diffractometry, which showed that the process is a single crystal-to-polycrystalline transformation involving a regular and progressive conversion of 1 into 2 with no obvious diffraction peaks that might be attributable to the intermediate cyclobutanol.

scholarly journals New Spiro-Tin Compounds: Reaction of N,N′-Dialkyl Sulfur Diimides with Cyclic Bis(amino)stannylenes - Unexpected Formation of a N-N Bond

1995 ◽  
Vol 50 (12) ◽  
pp. 1811-1817 ◽  
Author(s):  
Max Herberhold ◽  
Christian Köhler ◽  
Wolfgang Milius ◽  
Bernd Wrackmeyer
Keyword(s):  
Molecular Structure ◽  
Magnetic Resonance ◽  
Single Crystal ◽  
Structure Analysis ◽  
Membered Ring ◽  
Monoclinic Space Group ◽  
Unexpected Formation ◽  
Tin Compounds ◽  
X Ray ◽  
Tert Butyl

N,N′-Dialkyl sulfur diimides (1), R(NSN)R [R = Me (a), Et (b), nPr (c), nBu (d)] react with cyclic bis(amino)stannylenes such as 1,3-di-tert-butyl-4,4-dimethyl-1,3,4,2λ2-diazasilastannetedine (2) or 1,3-di-tert-butyl-4,4,5,5-tetramethyl-1,3,4,5,2λ2-diazadisilastannolidine (3) in a 2:1 ratio to give the new spiro-tin(IV) compounds 5a-d, 6b and 6c, built from the respective cyclic bis(amino)stannylene and a seven-membered ring in which the two sulfur diimide groups are coupled via a N-N bond and across the tin atom. A 1:1 adduct 4 is proposed as an intermediate which is the final product 4e in the case of R = tBu (1e). The products were characterized by multinuclear magnetic resonance (1H, 13C, 15N, 29Si, 119Sn NMR), and in the case of 5c the molecular structure was determined by single crystal X-ray structure analysis [monoclinic, space group C2/c ; a = 1504.1(3), b = 1393.3(3), c = 1688.6(3) pm; β = 115.71(3)°].

ChemInform Abstract: Dolastatins. Part 24. Synthesis of (-)-Dolastatin 10. X-Ray Molecular Structure of N,N-Dimethylvalyl-valyl-dolaisoleuine tert-Butyl Ester.

ChemInform ◽  
2010 ◽  
Vol 27 (33) ◽  
pp. no-no
Author(s):  
G. R. PETTIT ◽  
J. K. SRIRANGAM ◽  
S. B. SINGH ◽  
M. D. WILLIAMS ◽  
D. L. HERALD ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Butyl Ester ◽  
X Ray ◽  
Tert Butyl ◽  
Dolastatin 10

A structural and carbon-nitrogen bond rotation study of N,N,N',N',2,2-hexamethylpropanediamide

1983 ◽  
Vol 36 (9) ◽  
pp. 1865 ◽  
Author(s):  
SF Lincoln ◽  
AM Hounslow ◽  
NJ Maeji ◽  
TW Hambley ◽  
MR Snow ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Solid State ◽  
Kinetic Parameters ◽  
Methyl Groups ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bond Rotation ◽  
Nitrogen Bonds ◽  
Rotation Study ◽  
Nitrogen Bond

The molecular structure of N,N,N',N',2,2-hexamethylpropanediamide has been determined in the solid state by X-ray diffraction methods. The structure of Me2NCOCMe2CONMe2 may be broadly described as two planar Me2NCO entities intersecting at the tetrahedral -CMe2- site. The angle between the normals to the two Me2NCO planes is 104.6�, and the two oxygen atoms are disposed outwards from the molecule and away from each other. Proton (270-MHz) n.m.r. studies yield k(320 K) 32.0 � 3.2 s-1, ΔH‡ 69.5 � 0.4 kJ mol-1 and ΔS‡ 0.6 � 1.1 J K-1 mol-1 for rotation of the N-methyl groups about the carbon-nitrogen bonds in CD3NO2 solution. Similar magnitudes for the kinetic parameters characterizing this process are obtained in CDCl3, and CD3CN solutions.

Molecular structure and dynamics of C-1-adamantyl substituted N-unsubstituted pyrazoles studied by solid state NMR spectroscopy and X-ray crystallography

1997 ◽  
pp. 1867-1876 ◽  
Author(s):  
Rosa María Claramunt ◽  
María Dolores Santa María ◽  
Isabelle Forfar ◽  
Francisco Aguilar-Parrilla ◽  
María Minguet-Bonvehí ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Solid State ◽  
Nmr Spectroscopy ◽  
Solid State Nmr ◽  
X Ray ◽  
Solid State Nmr Spectroscopy ◽  
X Ray Crystallography ◽  
Structure And Dynamics

Behavior of 1,3-Di(tert-butyl)-2,4-bis(tetramethylpiperidino)-1,3,2,4-diphospha- diboretane towards Boron Halides and Adduct Formation of a Bicyclo[1.1.0]diphosphadiboretane with Tris(pentafluorophenyl)borane [1]

2006 ◽  
Vol 61 (3) ◽  
pp. 265-274 ◽  
Author(s):  
Klaus Knabel ◽  
Heinrich Nöth ◽  
Robert T. Paine
Keyword(s):  
Molecular Structure ◽  
Structure Analysis ◽  
Adduct Formation ◽  
Ring System ◽  
Lewis Acidity ◽  
X Ray ◽  
Tert Butyl ◽  
Boron Halides ◽  
System 2

AbstractWhile the diphosphadiboretane (tBuP=Btmp)2, 1, reacts with boron trihalides BX3 (X = Cl, Br, I) with BN cleavage producing a number of unidentifiable products, a new tricyclic BP ring system 2, containing B3P3, PB2C2 and C6 rings, results from the combination of PhBCl2 and 1. B-Chlorocatecholborane and 1 give access to the diborylphosphane 3, tmpBCl-PtBu-cat (cat = C6H4O2B). This shows that the selectivity of the reactions increases as the Lewis acidity of boron halide decreases. The structure of compounds 2 and 3 were determined by X-ray structure analysis. The bicyclic (tmpBP)2 4 forms no adducts with MeI, CF3SO2Me or Ph3C(SnCl5). However, it adds B(C6F5)3 to give 10, the first BX3 adduct of this bicycle that is fully characterized including its molecular structure.

Molecular structure in the solid state (X-Ray diffraction) and in solution (1H and 13C NMR) of nifurtimox and two pyrazol-1-Yl analogs

2010 ◽  
Vol 97 (11-12) ◽  
pp. 1055-1066 ◽  
Author(s):  
Ma de la Concepción Foces-Foces ◽  
Félix Hernández Cano ◽  
Rosa Ma Claramunt ◽  
Alain Fruchier ◽  
José Elguero
Keyword(s):  
Molecular Structure ◽  
Solid State ◽  
13C Nmr ◽  
X Ray Diffraction ◽  
1H And 13C Nmr ◽  
X Ray

Dolastatins 24: synthesis of (–)-dolastatin 10. X-Ray molecular structure of N,N-dimethylvalyl-valyl-dolaisoleuine tert-butyl ester

1996 ◽  
pp. 859-863 ◽  
Author(s):  
George R. Pettit ◽  
Jayaram K. Srirangam ◽  
Sheo Bux Singh ◽  
Michael D. Williams ◽  
Delbert L. Herald ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Butyl Ester ◽  
X Ray ◽  
Tert Butyl ◽  
Dolastatin 10
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