scholarly journals Triggering of the Bergman Cyclization by Photochemical Ring Contraction. Facile Cycloaromatization of Benzannulated Cyclodeca-3,7-diene-1,5-diynes

2007 ◽  
Vol 129 (13) ◽  
pp. 3792-3793 ◽  
Author(s):  
Grigori V. Karpov ◽  
Vladimir V. Popik
Keyword(s):  
Bergman Cyclization ◽  
Ring Contraction

Photochemical Triggering of the Bergman and Myers - Saito Cyclizations

2010 ◽  
Vol 63 (7) ◽  
pp. 1099 ◽  
Author(s):  
Andrei Polukhtine ◽  
Grigori Karpov ◽  
Dinesh R. Pandithavidana ◽  
Alexander Kuzmin ◽  
Vladimir V. Popik
Keyword(s):  
Triple Bond ◽  
Nuclease Activity ◽  
Membered Ring ◽  
Single Strand ◽  
The Other ◽  
Bergman Cyclization ◽  
Ring Contraction ◽  
Two Photon ◽  
Photochemical Generation ◽  
Photon Excitation

Two strategies for the photochemical generation of reactive enediyne compounds and their subsequent cycloaromatization to p-benzyne or α,3-didehydrotoluene derivatives are discussed in this account. The first method employs a photo-Wolff reaction of stable 11- or 12-membered ring precursor enediynes containing the 2-diazo-1,3-diketone moiety. Irradiation of these compounds results in ring contraction and the formation of two isomeric enediynes possessing an enolized β-ketoester fragment. One of the isomers undergoes the conventional Bergman cyclization, whereas the other isomerizes into the enyne-allene tautomer, which rapidly cyclizes via a Myers–Saito mechanism. The second strategy consists of replacing the triple bond in a cyclic enediyne or enyne-allene structure with a cyclopropenone group, rendering them thermally stable. Photolysis of cyclopropenones results in efficient decarbonylation and the regeneration of a triple bond, restoring the enediyne π-system. The generation of reactive enediynes by non-resonant two-photon excitation using wavelengths within a ‘phototherapeutic window’ was also demonstrated. Photogenerated enediynes show significant nuclease activity, efficiently inducing single-strand dDNA cleavage.

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

Synthesis of the Cyclopentyl Nucleoside (−)-Neplanocin A fromD-Glucosevia Zirconocene-Mediated Ring Contraction

2005 ◽  
Vol 88 (6) ◽  
pp. 1185-1198 ◽  
Author(s):  
Leo A. Paquette ◽  
Zhenjiao Tian ◽  
Christopher K. Seekamp ◽  
Tony Wang
Keyword(s):  
Ring Contraction ◽  
Neplanocin A

ChemInform Abstract: Ring Contraction of Sulfenamides Derived from Thiochroman-4-ones.

ChemInform ◽  
2010 ◽  
Vol 25 (21) ◽  
pp. no-no
Author(s):  
C. D. GABBUTT ◽  
J. D. HEPWORTH ◽  
B. M. HERON ◽  
M. KANJIA
Keyword(s):  
Ring Contraction
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