scholarly journals Qualitative evaluation of regioselectivity in the formation of di- and tri-6-O-tritylates of α-cyclodextrin

2015 ◽  
Vol 11 ◽  
pp. 1530-1540 ◽  
Author(s):  
Keisuke Yoshikiyo ◽  
Yoshihisa Matsui ◽  
Tatsuyuki Yamamoto
Keyword(s):  
Quantitative Analysis ◽  
Steric Hindrance ◽  
Nmr Spectra ◽  
Ring Current ◽  
Qualitative Evaluation ◽  
Reaction Products ◽  
H Nmr ◽  
Clockwise Direction

The quantitative analysis of reaction products showed that the reaction of 6A,6D-di-O-trityl-α-cyclodextrin (CD), AD-isomer, with trityl chloride in pyridine at 55 °C gave 6A,6B,6E-tri-O-trityl-α-CD, the amount of which was only 25% of that of simultaneously formed 6A,6B,6D-tri-O-trityl-α-CD. This indicates that the bulky trityl groups of glucopyranose-A and -D (Glu-A and -D, respectively) in the AD-isomer mainly retard the additional tritylation of the C(6)-OH of the adjacent glucopyranoses in a counter-clockwise direction (Glu-F and -C, respectively). 1H NMR spectra of the AD-isomer showed that the O(6)-H and C(6)-H signals of Glu-C and -F are shifted upfield due to the ring current of the trityl groups. Thus, it is concluded that the bulky trityl groups on Glu-A and Glu-D are oriented to Glu-F and Glu-C, respectively, and sterically retard additional tritylation on Glu-F and Glu-C. Similar steric hindrance was also observed in the additional tritylations of mono-6-O-trityl-α-CD, 6A,6B-di- and 6A,6C-di-O-trityl-α-CD’s.

A 15N, 13C, and 1H NMR study of reaction products from arylguanidines and chloroformate esters

1991 ◽  
Vol 56 (7) ◽  
pp. 1505-1511 ◽  
Author(s):  
Antonín Lyčka ◽  
Karel Palát
Keyword(s):  
1H Nmr ◽  
Nmr Spectra ◽  
Reaction Products ◽  
H Nmr ◽  
Nmr Study

The 15N, 13C, and 1H NMR spectra of the reaction products from arylguanidines with two mols of chloroformate esters have been measured. With application of the corresponding 15N isotopomer it has been proved that the reaction products have the structures IIIa-IIIc.

scholarly journals Darstellung, Struktur und einige Reaktionen von Tris(dimethylamino)gallan / Preparation, Structure and Some Reactions of Trisdimethylaminogallane

1975 ◽  
Vol 30 (9-10) ◽  
pp. 681-687 ◽  
Author(s):  
H. Nöth ◽  
P. Konrad
Keyword(s):  
Steric Hindrance ◽  
Nmr Spectra ◽  
Gallium Atom ◽  
H Nmr

The aminogallanes Ga[N(CH3)2]3 (1), ClGa[N(CH3)2]2 (2) and Ga[N(Si(CH3)3)2]3 (3) are prepared by reacting GaCl3 with LiN(CH3)2 and NaN[Si(CH3)3]2, respectively. Excess LiN(CH3)2 leads to LiGa[N(CH3)4] which reacts with GaCl3 to yield 1. CS2 inserts into all Ga—N bonds of 1 yielding monomeric Ga[S2CN(CH3)3)2]3 (4).1 dimerizes via dimethylamino bridges. In contrast, 1H. NMR spectra indicate group exchange for dimeric 2. Assoziation of 3 is prevented due to steric hindrance. The gallium atom in 4 exhibits hexacoordination, and there is evidence for the binding of the (CH3)2NCS2 groups through S atoms only.

Nitration and bromination of l,1-diphenyl-2-(2-thienyl)ethylene

1978 ◽  
Vol 56 (21) ◽  
pp. 2755-2757 ◽  
Author(s):  
Francesco A. Bottino ◽  
Giuseppe C. Pappalardo ◽  
Giuseppe Scarlata ◽  
Domenico Sciotto ◽  
Michele Torre
Keyword(s):  
Dipole Moment ◽  
Nmr Spectra ◽  
Reaction Products ◽  
H Nmr

The behaviour of 1,1-diphenyl-2-(2-thienyl)ethylene towards electrophilic agents (Br2, HNO3) has been investigated and the structure of reaction products assigned by uv, 1H nmr spectra, and dipole moment measurements.

Photoreaktionen von Dekacarbonyldirhenium mit Allen und unverzweigten Allenderivaten / Photoreactions of Decacarbonyldirhenium with Allene and Unbranched Derivatives of Allene

1995 ◽  
Vol 50 (4) ◽  
pp. 649-660 ◽  
Author(s):  
Cornelius G. Kreiter ◽  
Wolfgang Michels ◽  
Gerhard Heeb
Keyword(s):  
Nmr Spectra ◽  
Crystal And Molecular Structure ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Oxidative Rearrangement ◽  
Dirhenium Complexes ◽  
Derivatives Of ◽  
By Products

Decacarbonyldirhenium (1) reacts upon UV irradiation with allene (2), 1,2-butadiene (3) and 2,3-pentadiene (4) preferentially by CO substitution and oxidative rearrangement to the corresponding enneacarbonyl-μ-η1:3-endiyl-dirhenium complexes 5, 9, and 15 and to the octacarbonyl-μ-η2:2-allene-dirhenium complexes 6, the stereoisomers 10, 11, and 16. At elevated temperature 5, 9, and 15 loose CO and yield by a reductive rearrangement also the complexes 6, 10, 11, and 16. In addition to these main products, depending upon the allene derivative used, various by-products are obtained.By-products of the reaction o f 1 with 2 are octacarbonyl-μ-η3:3-(2,3-dimethylene-buta-1,4- diyl)dirhenium (7) and μ-η2:2-allene-hexacarbonyl-μ-η1:3-1-propene-1,3-diyl-dirheniurn (8). The photo reaction of 1 with 3 yields, in addition to 9-11, tetracarbonyl-η3-(E-5-ethylidene- 4-methyl-2-cyclopenten-1-yl)rhenium (12) and tetracarbonyl-η3-(Z-5-ethyliden-4- methyl-2-cyclopenten-1-yl)rhenium (13) as a mixture of isomers. 1 and 4 form the by-products tetracarbonyl-η3-(EZ-3-penten-2-yl)rhenium (17), tetracarbonyl-η3-(EE-3-penten-2-yl)rhenium (18) and heptacarbonyl-μ-η1:2:1:2-(4,5-dimethyl-2,6-octadiene-3,6-diyl)dirhenium (19) with an unusually bridging and chelating ligand. The constitutions of the reaction products have been concluded from the IR and 1H NMR spectra. For 19 the crystal and molecular structure has been determined by X-ray diffraction analysis.

On the Stereoselectivity of the (-)-Dimenthyl Malonate Addition to α,β-Unsaturated Ketones

1996 ◽  
Vol 61 (12) ◽  
pp. 1805-1814 ◽  
Author(s):  
Ľubomír Šebo ◽  
Juraj Alföldi ◽  
Grety Rihs ◽  
Štefan Toma
Keyword(s):  
Michael Addition ◽  
Pure State ◽  
Nmr Spectra ◽  
Reaction Products ◽  
X Ray ◽  
Unsaturated Ketones ◽  
H Nmr ◽  
The Michael Addition

The Michael addition of (-)-dimenthyl malonate to eight α,β-unsaturated ketones has been studied. The ratio of diastereomers was calculated on the basis of the 1H NMR spectra of the crude reaction products. The diastereomer excess varied from 10 to 50%, depending on the structure of the starting enone. The pure diastereomer produced by addition of (-)-dimenthyl malonate to 2-benzylidene-1,4-indandione was isolated by repeated crystallization. X-ray analysis has shown that the isomer is (-)-dimenthyl (R)-2-[1-(1,3-dioxoindan-2-yl)-1-phenylmethyl]malonate (5a). The predominating diastereomers of (-)-dimenthyl(3-ferrocenyl-3-oxophenylpropyl)malonate (1a) and (-)-dimenthyl-2-(1-(1,3-dioxo[3]ferrocenophan-2-yl)-1-phenyl malonate (6a) were also isolated in pure state by careful crystallization.

Some reactions of trimeric silicon phthalocyanine under alkaline conditions

2003 ◽  
Vol 07 (03) ◽  
pp. 176-180 ◽  
Author(s):  
Viktor N. Myakov ◽  
Vyacheslav A. Kuropatov ◽  
Tatyana I. Lopatina ◽  
Valentina N. Sedelnikova
Keyword(s):  
Nmr Spectroscopy ◽  
Spectroscopic Study ◽  
Nmr Spectra ◽  
Ring Current ◽  
Electron System ◽  
Absorption Bands ◽  
H Nmr ◽  
Alkaline Conditions ◽  
Silicon Phthalocyanine

The reaction of bis(trimethylsiloxy)triphthalocyaninatosilicon, Me 3 Si ( OSiPc )3 OSiMe 3 ( Pc 3) with KOH in o-xylene in the presence of 15-crown-5 in vacuum at 200°C has been studied by means of UV-vis, EPR and 1 H NMR spectroscopy. Upon gradual removal of H 2 O , the formation of mono- and dianions of Pc 3 with absorption bands positioned at 575-590 nm was observed. An EPR spectroscopic study revealed that both monoanionic and dianionic of Pc 3 are paramagnetic in solution. 1 H NMR spectra have shown the absence of a ring current in the π-electron system of dianion. The reaction of Pc 3 with KOH or metal Na led to degradation of the Si - O - Si - backbone happened.

Some reactions of dimeric silicon phthalocyanines under alkaline conditions

2002 ◽  
Vol 06 (05) ◽  
pp. 336-339 ◽  
Author(s):  
Viktor N. Myakov ◽  
M. A. Lopatin ◽  
Yu. A. Kurskii
Keyword(s):  
Nmr Spectroscopy ◽  
Crown Ether ◽  
Nmr Spectra ◽  
Ring Current ◽  
Electron System ◽  
H Nmr ◽  
Silicon Phthalocyanines ◽  
Alkaline Conditions

Reactions of bis(hydroxy)- and bis(trimethylsiloxy)diphthalocyaninato silicon with KOH were studied in o-xylene or oligosiloxane in the presence of crown ether 15-cr-5 in vacuo at 190-200 °C by the means of electronic, EPR and 1 H NMR spectroscopy. Under gradual removing of H 2 O , consecutive formation of paramagnetic silicon diphthalocyanine monoanions (λ max 580 nm ), and diamagnetic silicon diphthalocyanine dianions (λ max 550 nm ) have been observed. The dianions react with H 2 O to regenerate silicon diphthalocyanine monoanions and then the starting silicon diphthalocyanine. Reaction of the dianion with O 2 results in a decomposition of silicon diphthalocyanine. 1 H NMR spectra of silicon diphthalocyanine dianion have proven the absence of a ring current in the π-electron system of the dianion.

Carbon-13 nuclear magnetic resonance spectra of E-silyl-alkenes

1980 ◽  
Vol 58 (4) ◽  
pp. 361-368 ◽  
Author(s):  
Constantinos A. Tsipis ◽  
Constantinos A. Tsoleridis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Quantitative Analysis ◽  
Nmr Spectroscopy ◽  
Carbon Atom ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
H Nmr ◽  
Nuclear Magnetic Resonance Spectra ◽  
C Nmr

Carbon-13 nmr chemical shifts of a number of E-silyl-alkenes containing the silyl substituent at an sp2 carbon atom are presented. Assignments of the chemical shifts have been made by noting systematic variations in the spectra with changes in substituents and by comparison of the chemical shifts to those of the corresponding unsubstituted alkenes. The substituent effects observed were explained on the basis of the π-acceptor ability of the silyl substituents and the structure of the molecules. Comparing the 13C nmr spectra of the E-silyl-alkenes and those of the corresponding unsubstituted alkenes, differential chemical shifts have been obtained which can be used as empirical substituent parameters for the prediction of the 13C nmr spectra of other E-silyl-alkenes not yet studied. It was also demonstrated that 13C nmr spectroscopy can be used without resorting to special techniques (gated decoupling and the addition of paramagnetics) as an alternative method to the 1H nmr for the quantitative analysis of mixtures of regio-isomer E-silyl-alkenes.

Darstellung, 11B-, 13C-, 1H-NMR-Spektren und Schwingungsspektren von 1,2-Xylylen-pentahydro-closo-hexaborat,cis-[B6H5(CH2)2C6H4]- , sowie Kristallstrukturen von cis-[P(C6H5)4][B6H5(CH2)2C6H4] und cis-[(n-C4H9)4N][B6H5(CH2)2C6H4] / Preparation, 11B, 13C, 1H NMR Spectra and Vibrational Spectra of 1,2-Xylylene-pentahydro-closo-hexaborate, cis-[B6H5(CH2)2C6H4]-, and the Crystal Structures of cis-[P(C6H5)4][B6H5(CH2)2C6H4] and cis-[(n-C4H9)4N ][B6H5(CH2)2C6H4]

1996 ◽  
Vol 51 (5) ◽  
pp. 691-697 ◽  
Author(s):  
W. Lübbe ◽  
W. Preetz
Keyword(s):  
Crystal Structures ◽  
1H Nmr ◽  
Nmr Spectra ◽  
Exchange Chromatography ◽  
Monoclinic Space Group ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Diethylaminoethyl Cellulose

By reaction of [B6H6]2- with ω,ω′-dibromo-o-xylene in acetonitrile the 1,2-xylylenepentahydro-closo-hexaborat, cis-[B6H5(CH2)2C6H4]- , is formed. The new ansa compound has been separated from excess [B6H6]2- and other reaction products by ion exchange chromatography on diethylaminoethyl cellulose. The crystal structures of cis-[P(C6H5)4][B6H5(CH2)2C6H4] (I) and as-[(n-C4H9)4N][B6H5(CH2)2C6H4] (II) have been determined by single crystal X-ray diffraction analysis: I is monoclinic, space group P 21/n with a = 13.715(5), b = 11.118(1) and c = 19.702(2) Å, β = 103.47(2)°; II is orthorhombic with a = 10.204(7), b = 13.352(4) and c = 20.824(8) Å. The 11B NMR spectrum confirms the structure with a hetero disubstituted octahedral B6 cage with local C2v symmetry. The 13C and 1H NMR spectra have been assigned in term of such a configuration. The IR and Raman spectra exhibit characteristic CH, BH, BC, B6 and arene vibrations.

scholarly journals Synthesis and characterization of π–extended “earring” subporphyrins

2018 ◽  
Vol 14 ◽  
pp. 1956-1960 ◽  
Author(s):  
Haiyan Guan ◽  
Mingbo Zhou ◽  
Bangshao Yin ◽  
Ling Xu ◽  
Jianxin Song
Keyword(s):  
Single Crystal ◽  
Aromatic Ring ◽  
Nmr Spectra ◽  
Ring Current ◽  
Synthesis And Characterization ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Single Crystal Structures

A π-extended “earring” subporphyrin 3 was synthesized from β,β′-diiodosubporphyrin and diboryltripyrrane via a Suzuki–Miyaura coupling and following oxidation. Its Pd complex 3Pd was also synthesized and both of the compounds were fully characterized by 1H NMR, MS and X-ray single crystal diffraction. The 1H NMR spectra and single crystal structures revealed that aromatic ring current did not extend to the “ear” in both of the two compounds. Their UV–vis/NIR spectra were recorded and the absorption of both compounds is extended to the NIR region and that the absorption of 3Pd is further red-shifted and more intense.

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