scholarly journals Photochemical electrocyclic ring closure and leaving group expulsion from N-(9-oxothioxanthenyl)benzothiophene carboxamides

2013 ◽  
Vol 12 (2) ◽  
pp. 309-322 ◽  
Author(s):  
Majher I. Sarker ◽  
Tasnuva Shahrin ◽  
Mark G. Steinmetz ◽  
Qadir K. Timerghazin
Keyword(s):  
Ring Closure ◽  
Leaving Group

DENSITY FUNCTIONAL STUDY OF SELECTED MONO-ZINC AND GEM-DIZINC RADICAL CARBENOID CYCLOPROPANATION REACTIONS: OBSERVATION OF AN EFFICIENT RADICAL ZINC CARBENOID CYCLOPROPANATION REACTION AND THE INFLUENCE OF THE LEAVING GROUP ON RING CLOSURE

2003 ◽  
Vol 02 (03) ◽  
pp. 357-369 ◽  
Author(s):  
CUNYUAN ZHAO ◽  
DONG-QI WANG ◽  
DAVID LEE PHILLIPS
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Radical Reaction ◽  
Ring Closure ◽  
Functional Study ◽  
Reaction Step ◽  
Leaving Group ◽  
Reaction Barriers ◽  
Leaving Groups ◽  
Zinc Carbenoid

We report a theoretical study of the cyclopropanation reactions of EtZnCHI, (EtZn)2CH EtZnCHZnI, and EtZnCIZnI radicals with ethylene. The mono-zinc and gem-dizinc radical carbenoids can undergo cyclopropanation reactions with ethylene via a two-step reaction mechanism similar to that previously reported for the CH2I and IZnCH2 radicals. The barrier for the second reaction step (ring closure) was found to be highly dependent on the leaving group of the cyclopropanation reaction. In some cases, the (di)zinc carbenoid radical undergoes cyclopropanation via a low barrier of about 5–7 kcal/mol on the second reaction step and this is lower than the CH2I radical reaction which has a barrier of about 13.5 kcal/mol for the second reaction step. Our results suggest that in some cases, zinc radical carbenoid species have cyclopropanation reaction barriers that can be competitive with their related molecular Simmons-Smith carbenoid species reactions and produce somewhat different cyclopropanated products and leaving groups.

Critical importance of leaving group ‘softness’ in nucleophilic ring closure reactions of ambident anions to 1,2-diazetidines

2010 ◽  
Vol 51 (2) ◽  
pp. 382-384 ◽  
Author(s):  
Michael J. Brown ◽  
Guy J. Clarkson ◽  
David J. Fox ◽  
Graham G. Inglis ◽  
Michael Shipman
Keyword(s):  
Ring Closure ◽  
Critical Importance ◽  
Leaving Group ◽  
Ambident Anions

Further Synthetic Applications of Functionalized 1,3-Dipoles

1975 ◽  
Vol 53 (24) ◽  
pp. 3782-3790 ◽  
Author(s):  
J. William Lown ◽  
B. Erik Landberg
Keyword(s):  
Ring Closure ◽  
Ethyl Diazoacetate ◽  
Fused Heterocycles ◽  
Leaving Group ◽  
Nitrile Imines ◽  
Azomethine Imines

Reactions of nitrile imines, azomethine imines, and ethyl diazoacetate (as representatives of functionalized 1,3-dipoles) with reactive olefins lead to a series of novel fused heterocycles after suitable ring closure. The influence of the nature of the heterocyclic leaving group and the substituents in the phenacyl residue in a group of phenacylimidazolium salts on the course of their reaction to produce 1,2-dihydrofurans and perhydropyrazolopyrroles is investigated.

scholarly journals 1,3-Dimethyl-3′,5-diphenyl-1,5-dihydro-2H,5′H-spiro[furo[2,3-d]pyrimidine-6,4′-isoxazole]-2,4,5′(3H)-trione

Molbank ◽  
10.3390/m1317 ◽  
2022 ◽  
Vol 2022 (1) ◽  
pp. M1317
Author(s):  
Yuliya E. Ryzhkova ◽  
Varvara M. Kalashnikova ◽  
Fedor V. Ryzhkov ◽  
Michail N. Elinson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Infrared Spectroscopy ◽  
Magnetic Resonance ◽  
Elemental Analysis ◽  
Sodium Acetate ◽  
Room Temperature ◽  
Halogen Atom ◽  
Ring Closure ◽  
Leaving Group ◽  
Intramolecular Ring

Michael addition–halogenation–intramolecular ring-closing (MHIRC) reactions are processes in which a halogen atom as a leaving group can attach to substrates or reactants during the reaction, which then undergoes intramolecular ring closure. In this communication the MHIRC transformation of 4-benzylidene-3-phenylisoxazol-5(4H)-one and 1,3-dimethylbarbituric acid in the presence of N-bromosuccinimide and sodium acetate in EtOH at room temperature was carefully investigated to give novel 1,3-dimethyl-3′,5-diphenyl-1,5-dihydro-2H,5′H-spiro[furo[2,3-d]pyrimi- dine-6,4′-isoxazole]-2,4,5′(3H)-trione in a good yield. The structure of the new compound was confirmed by the results of elemental analysis as well as mass, nuclear magnetic resonance, and infrared spectroscopy.

Folding strain stereocontrol in cyclohexane ring formation by means of an intramolecular ester enolate alkylation reaction

1996 ◽  
Vol 74 (12) ◽  
pp. 2487-2502 ◽  
Author(s):  
Takashi Tokoroyama ◽  
Hisashi Kusaka
Keyword(s):  
Stereoselective Synthesis ◽  
High Selectivity ◽  
Ring Closure ◽  
Alkylation Reaction ◽  
Qualitative Comparison ◽  
Enolate Alkylation ◽  
Leaving Group ◽  
Counter Cation ◽  
Ester Enolate ◽  
C Nmr

Diastereoselectivity in the cyclization of ethyl 7-bromo-2-methylheptanoates with an additional substituent at various positions in the chain, by LDA treatment, was investigated in connection with the concept of folding strain stereocontrol. Cyclization of 3-, 4-, and 6-methyl-substituted substrates revealed high selectivity, which demonstrates the prevalence of folding strain stereocontrol and the usefulness of this approach for stereoselective ring construction. In particular, reactions of the latter two substrates resulted in the stereodivergent preparation of diastereomeric 1,3-dimethylcyclohexanecarboxylates. In the case of the 5-mefhyl-substituted substrate, the selectivity of ring closure was only moderate. 1H and 13C NMR spectroscopic data were useful for determining the conformation of 1 -methylcyclohexanecarboxylate derivatives. The origin of the diastereoselectivity was examined through the qualitative comparison of the strain in the diastereomeric folding in the transition state. Various factors that might affect stereoselectivity were examined in the cyclization of 5-substituted substrates to better understand this concept. As predicted, the selectivity increased as the substituent became bulkier: Ph < Me ≈ Et < i-Pr < t-Bu. The effects of other factors — solvent, base counter cation, and leaving group — on selectivity agree with results predicted from the reactivity–selectivity relationship. Key words: folding strain stereocontrol; diastereoselectivity in ring-closure reaction; remote asymmetric induction; ethyl 2-methylcyclohexanecarboxylate derivatives, 1H and 13C NMR; stereoselective synthesis of substituted cyclohexane derivatives.

General Cyclopropane Assembly via Enantioselective Redox-Active Carbene Transfer to Aliphatic Olefins

2018 ◽  
Author(s):  
Marc Montesinos-Magraner ◽  
Matteo Costantini ◽  
Rodrigo Ramirez-Contreras ◽  
Michael E. Muratore ◽  
Magnus J. Johansson ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Asymmetric Synthesis ◽  
Chemical Space ◽  
Synthetic Approach ◽  
Asymmetric Cyclopropanation ◽  
Redox Active ◽  
Wide Range ◽  
Leaving Group ◽  
Stereoelectronic Properties ◽  
Carbene Transfer

Asymmetric cyclopropane synthesis currently requires bespoke strategies, methods, substrates and reagents, even when targeting similar compounds. This limits the speed and chemical space available for discovery campaigns. Here we introduce a practical and versatile diazocompound, and we demonstrate its performance in the first unified asymmetric synthesis of functionalized cyclopropanes. We found that the redox-active leaving group in this reagent enhances the reactivity and selectivity of geminal carbene transfer. This effect enabled the asymmetric cyclopropanation of a wide range of olefins including unactivated aliphatic alkenes, enabling the 3-step total synthesis of (–)-dictyopterene A. This unified synthetic approach delivers high enantioselectivities that are independent of the stereoelectronic properties of the functional groups transferred. Our results demonstrate that orthogonally-differentiated diazocompounds are viable and advantageous equivalents of single-carbon chirons<i>.</i>

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