Untersuchungen zur Ringkontraktion am 1,4-Dithia-2,6-diaza-3,5-diborinan-System/ Studies on Ring Contraction of the l,4-Dithia-2,6-diaza-3,5-diborinane System

1988 ◽  
Vol 43 (8) ◽  
pp. 959-962 ◽  
Author(s):  
Carl Habben ◽  
Anton Meiler ◽  
Stefan Pusch
Keyword(s):  
Mass Spectra ◽  
Ring System ◽  
Membered Ring ◽  
Ring Contraction ◽  
C Nmr

AbstractThe 1,4-dithia-2,6-diaza-3,5-diborinanes 1a-d react with elemental sodium with formation of the 1,3-diaza-2,4-diboretidines 2a-d. By use of more sodium in case of 1 d or 3,5-bis(diethylamino)- 2-cyclohexyl-6-trimethylsilyldiborinane, the 1,3-thiaza-2,4-diboretidines 3 were formed. 3.5-Dimethyl-2,6-bis(trimethylsilyl)-1,4-dithia-2,6-diaza-3,5-diborinane gives the borazine 4, The reaction of di-t-butyl-sulfurdiimide with 2,6-di-t-butyl-3,5-dimethyl-1,4-dithia-2,6-diaza-3,5-diborinane leads by ring contraction to the four-membered ring system 5. 1H, 11B, 13C NMR and mass spectra are reported and discussed.

Formen des Diphenylgermaniumoxids(Ph2GeO)x, x = 3, 4, n / Phases of Diphenylgermanium Oxide(Ph2GeO)x, x = 3, 4, n

1984 ◽  
Vol 39 (7) ◽  
pp. 868-875 ◽  
Author(s):  
Ludwig Roß ◽  
Martin Dräger
Keyword(s):  
Crystal Structure ◽  
Thermal Analysis ◽  
Vibrational Spectra ◽  
Mass Spectra ◽  
Nmr Spectra ◽  
Membered Ring ◽  
Tetragonal Crystals ◽  
Hydroxy Groups ◽  
C Nmr

Diphenylgermanium oxide can be obtained trimeric (6 -membered ring, monoclinic crystals), tetrameric (8 -membered ring, monoclinic and tetragonal crystals and monoclinic with half a mole of crystal ethanol) and polymeric with terminating hydroxy groups. Transitions are investigated by thermal analysis, mass spectra and 13C NMR spectra. The vibrational spectra (I. R . and Raman) of the forms are discussed . The crystal structure of the monoclinic (Ph :GeO)4 has been determined and refined to R = 0.051. The symmetry of the molecule is near to S4 (distances Ge - O 174.7 - 176.2, Ge - C 190.0 - 194.6 pm, angles Ge - O - Ge 131.2 - 136.9, O - Ge - O 107.8 -110.3 °).

Bicyclo[2.2.2]octane-2-spirocyclohexanes, Part 3. Synthesis and Reactions of Mono- and Dibromospirodiisophoranes

1992 ◽  
Vol 47 (1) ◽  
pp. 126-138 ◽  
Author(s):  
Frederick Kurzer ◽  
Zakir Kapadia
Keyword(s):  
Nmr Spectra ◽  
Ring System ◽  
Lithium Aluminium Hydride ◽  
Ring Contraction ◽  
Lithium Aluminium ◽  
The Individual ◽  
C Nmr

Halogenation by the appropriate amounts of bromine or N-bromosuccinimide converts spirodiisophora-3',6-dione successively into the 4'-ax-mono- and 2',4'-diax-dibromo-3',6-dione. The latter is reduced by lithium aluminium hydride to the corresponding 6,3'-ketol. with retention of one or both bromo-substituents, depending on conditions. The bromoketones undergo the Favorski ring-contraction under the influence of alkalis to compounds of the bicyclo[2.2.2]octane-2-spirocyclopentane ring-system . The 13C NMR spectra of the individual products are assigned and correlated with their structures.

Synthesis of 2-amino-5,7-dimethyl-4-oxopyrido[3,4-e]-1,3-thiazines

1983 ◽  
Vol 48 (12) ◽  
pp. 3426-3432 ◽  
Author(s):  
Dušan Koščík ◽  
Pavol Kristian ◽  
Ondrej Forgáč
Keyword(s):  
Spectral Data ◽  
Chlorine Atom ◽  
Mass Spectra ◽  
High Reactivity ◽  
Secondary Amines ◽  
Dimroth Rearrangement ◽  
H Nmr ◽  
New Synthesis ◽  
C Nmr

New synthesis of pyrido[3,4-e]-1,3-thiazines consisting in reaction of 2,6-dimethyl-4-chloronicotinoyl isothiocyanate with primary or secondary amines, or with benzaldehyde phenylhydrazone, is described. High reactivity of the chlorine atom does not allow isolation of the corresponding thioureas, arising as intermediates, except in the case of the benzylamino derivative. Structure of the products was unequivocally confirmed by their spectral data (IR, UV, 1H NMR, 13C NMR and mass spectra). The synthesized derivatives do not undergo the Dimroth rearrangement.

Oxynemorensine, an alkaloid from Senecio nemorensis L., var. subdecurrens GRISEB

1980 ◽  
Vol 45 (2) ◽  
pp. 548-558 ◽  
Author(s):  
Antonín Klásek ◽  
Petr Sedmera ◽  
Jindřich Vokoun ◽  
Anna Boeva ◽  
Svatava Dvoráčková ◽  
...  
Keyword(s):  
Unsaturated Acid ◽  
Mass Spectra ◽  
H Nmr ◽  
C Nmr

From S. nemorensis L., var. subdecurrens GRISEB. there were isolated the previously obtained alkaloids nemorensine (I), retroisosenine (II), bulgarsenine (III) and, in addition, the alkaloid oxynemorensine which was assigned the structure VIII on the basis of the interpretation of the 1H-NMR, 13C-NMR, mass spectra, and on that of the identification of the products of hydrolysis and reduction. Furthermore, the isolation of the cis-nemorensic acid (V) as well as that of the unsaturated acid IV, and the transformation of bulgarsenine (III) to nemorensine (I) were described.

ChemInform Abstract: [3,3]-Sigmatropic Rearrangement/Allylboration/Cyclization Sequence: Enantioenriched Seven-Membered-Ring Carbamates and Ring Contraction to Pyrrolidines.

ChemInform ◽  
2016 ◽  
Vol 47 (21) ◽  
Author(s):  
Aurelie Mace ◽  
Sabrina Touchet ◽  
Patricia Andres ◽  
Fernando Cossio ◽  
Vincent Dorcet ◽  
...  
Keyword(s):  
Sigmatropic Rearrangement ◽  
Membered Ring ◽  
Ring Contraction

Mass spectra of some substituted methylcyclosiloxanes

1983 ◽  
Vol 61 (4) ◽  
pp. 762-768 ◽  
Author(s):  
E. Pelletier ◽  
J. F. Harrod
Keyword(s):  
Mass Spectra ◽  
Ring Contraction

The mass spectra of the substituted methylcyclosiloxanes [Formula: see text] where X = H (n = 4, 5 and 6), X = C6H5 (n = 3 and 4), X = Br (n = 3 and 4), X = Co(CO)4 (n = 4 and 5) have been measured. The compounds X = H fragment by the same kinds of substituent loss and ring contraction mechanisms as previously reported for the compounds X = CH3 but also by the loss of methylhydrogensilanone. The compounds X = Ph fragment by loss of benzene from an intramolecularly bridging benzenonium ion, formed from [M − CH3]+• and by losses of the phenylmethylsilanone fragments. The compounds X = Br only undergo substituent loss without ring fragmentation. The compounds X = Co(CO)4 show stepwise loss of all CO groups from [M]+•, [M − Co(CO)4]+, and [M]++.

Diazabenzenes. I. Synthesis of some t-butylpyrazines and their N-oxides

1972 ◽  
Vol 25 (12) ◽  
pp. 2671 ◽  
Author(s):  
RF Evans ◽  
KN Mewett
Keyword(s):  
Steric Hindrance ◽  
Mass Spectra ◽  
Ammonium Acetate ◽  
Spectroscopic Properties ◽  
Iron Pentacarbonyl ◽  
Membered Ring ◽  
Low Resolution ◽  
Butyl Lithium ◽  
Pyrazine Ring ◽  
Resolution Mass

Steric hindrance prevented formation of tetra-t-butylpyrazine either when pivaloin was heated with ammonium acetate or when pivalil monooxime was reduced with zinc and alkali. Diminution of the steric hindrance of the t-butyl groups by masking them by incorporation into a seven-membered ring containing sulphur was of no avail. 2,5-Di-t- butylpyrazine resulted from the analogous reduction of t-butyl-glyoxal dioxime and could be converted into its N-oxide and N,N?-dioxide. t- Butyl-lithium reacted with the pyrazine and the mono-N-oxide to give a mixture of products including 2,3,5-tri-t-butylpyrazine whose spectroscopic properties suggested a buckling of the pyrazine ring. Benzonitrile and diphenylacetylene reacted independently in the presence of iron pentacarbonyl and gave, inter alia, 2,4,6-triphenyl- 1,3,5-triazine and hexaphenylbenzene respectively. ��� The most prominent features of the low resolution mass spectra of these pyrazines and some of their precursors are discussed and rationalized.

scholarly journals Homocoupling Reactions of Azoles and Their Applications in Coordination Chemistry

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5950
Author(s):  
Steffen B. Mogensen ◽  
Mercedes K. Taylor ◽  
Ji-Woong Lee
Keyword(s):  
Coordination Chemistry ◽  
Reaction Mechanisms ◽  
Metal Organic Frameworks ◽  
Ring System ◽  
Membered Ring ◽  
Materials Chemistry ◽  
Structural Class ◽  
Basic Nitrogen ◽  
Metal Organic ◽  
Metal Catalyzed

Pyrazole, a member of the structural class of azoles, exhibits molecular properties of interest in pharmaceuticals and materials chemistry, owing to the two adjacent nitrogen atoms in the five-membered ring system. The weakly basic nitrogen atoms of deprotonated pyrazoles have been applied in coordination chemistry, particularly to access coordination polymers and metal-organic frameworks, and homocoupling reactions can in principle provide facile access to bipyrazole ligands. In this context, we summarize recent advances in homocoupling reactions of pyrazoles and other types of azoles (imidazoles, triazoles and tetrazoles) to highlight the utility of homocoupling reactions in synthesizing symmetric bi-heteroaryl systems compared with traditional synthesis. Metal-free reactions and transition-metal catalyzed homocoupling reactions are discussed with reaction mechanisms in detail.

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