Intramolecular rearrangement with ring contraction of 1,4-dihydroxy-3-bromo-2,2,6,6-tetramethylpiperidine

1987 ◽  
Vol 36 (7) ◽  
pp. 1461-1466
Author(s):  
L. A. Krinitskaya ◽  
N. L. Zaichenko ◽  
B. V. Rozynov ◽  
S. R. Osmanova
Keyword(s):  
Intramolecular Rearrangement ◽  
Ring Contraction

ChemInform Abstract: Intramolecular Rearrangement with Ring Contraction of 1,4-Dihydroxy-3- bromo-2,2,6,6-tetramethylpiperidine.

ChemInform ◽  
1988 ◽  
Vol 19 (8) ◽  
Author(s):  
L. A. KRINITSKAYA ◽  
N. L. ZAICHENKO ◽  
B. V. ROZYNOV ◽  
S. R. OSMANOVA
Keyword(s):  
Intramolecular Rearrangement ◽  
Ring Contraction

Thermo-Oxidative Decomposition of Lovage (Levisticum officinale) and Davana (Artemisia pallens) Essential Oils under Simulated Tobacco Heating Product Conditions

2020 ◽  
Vol 29 (1) ◽  
pp. 27-43
Author(s):  
Emma Jakab ◽  
Zoltán Sebestyén ◽  
Bence Babinszki ◽  
Eszter Barta-Rajnai ◽  
Zsuzsanna Czégény ◽  
...  
Keyword(s):  
Low Temperature ◽  
Essential Oils ◽  
Relative Yield ◽  
Gas Chromatography Mass Spectrometry ◽  
Intramolecular Rearrangement ◽  
Oxidation Reactions ◽  
Pyrolysis Gas ◽  
Oxidative Decomposition ◽  
Oxidative Pyrolysis ◽  
Artemisia Pallens

SummaryThe thermo-oxidative decomposition of lovage (Levisticum officinale) and davana (Artemisia pallens) essential oils has been studied by pyrolysis-gas chromatography/mass spectrometry in 9% oxygen and 91% nitrogen atmosphere at 300 °C to simulate low-temperature tobacco heating conditions. Both lovage and davana oils contain numerous chemical substances; the main components of both oils are various oxygen-containing compounds. Isobenzofuranones are the most important constituents of lovage oil, and their relative intensity changed significantly during oxidative pyrolysis. (Z)-ligustilide underwent two kinds of decomposition reactions: an aromatization reaction resulting in the formation of butylidenephthalide and the scission of the lactone ring with the elimination of carbon dioxide or carbon monoxide. Davanone is the main component of davana oil, which did not decompose considerably during low-temperature oxidative pyrolysis. However, the relative yield of the second most intensive component, bicyclogermacrene, reduced markedly due to bond rearrangement reactions. Davana ether underwent oxidation reactions leading to the formation of various furanic compounds. The changes in the composition of both essential oils could be interpreted in terms of bond splitting, intramolecular rearrangement mechanisms and oxidation reactions of several constituents during low-temperature oxidative pyrolysis. The applied thermo-oxidative method was found to be suitable to study the stability of the essential oils and monitor the decomposition products under simulated tobacco heating conditions. In spite of the complicated composition of the essential oils, no evidence for interaction between the oil components was found. [Beitr. Tabakforsch. Int. 29 (2020) 27–43]

The Influence of Anomeric Configuration and Aglycone Structure on the Outcome of Acid‐Promoted Ring Contraction in 2,3‐Di‐ O ‐Silylated S‐Galactopyranosides

2021 ◽  
Vol 6 (24) ◽  
pp. 6223-6229
Author(s):  
Polina I. Abronina ◽  
Alexander I. Zinin ◽  
Nelly N. Malysheva ◽  
Maxim Y. Karpenko ◽  
Natalya G. Kolotyrkina ◽  
...  
Keyword(s):  
Ring Contraction ◽  
Anomeric Configuration

N-Chlorinative Ring Contraction of 1,4-Dimethoxyphthalazines via a Bicyclization/Ring-Opening Mechanism

Synthesis ◽  
2020 ◽  
Author(s):  
Jeong Kyun Im ◽  
Ilju Jeong ◽  
Jun-Ho Choi ◽  
Won-jin Chung ◽  
ByeongDo Yang ◽  
...  
Keyword(s):  
Ring Opening ◽  
Reaction Conditions ◽  
Ring Contraction ◽  
Silyl Group ◽  
Favorskii Rearrangement ◽  
Mechanistic Analysis ◽  
Group A ◽  
Overall Efficiency ◽  
Trichloroisocyanuric Acid

AbstractAn unprecedented N-chlorinative ring contraction of 1,2-diazines was discovered and investigated with an electrophilic chlorinating reagent, trichloroisocyanuric acid (TCICA). Through optimization and mechanistic analysis, the assisting role of n-Bu4NCl as an exogenous nucleophile was identified, and the optimized reaction conditions were applied to a range of 1,4-dimethoxyphthalazine derivatives. Also, an improvement of overall efficiency was demonstrated by the use of a labile O-silyl group. A bicyclization/ring-opening mechanism, inspired by the Favorskii rearrangement, was proposed and supported by the DFT calculations. Furthermore, the efforts on scope expansion as well as the evaluation of other electrophilic promoters revealed that the newly developed ring contraction reactivity is a unique characteristic of 1,4-dimethoxyphthalazine scaffold and TCICA.

scholarly journals Ring Contraction by NHC‐Induced Pnictogen Abstraction

2019 ◽  
Vol 58 (46) ◽  
pp. 16563-16568 ◽  
Author(s):  
Martin Piesch ◽  
Stephan Reichl ◽  
Michael Seidl ◽  
Gábor Balázs ◽  
Manfred Scheer
Keyword(s):  
Ring Contraction
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