Search results for "Aryne"

Diels-Alder-Reaktionen von Vinylindolen mit Arin und 1,4-Benzochinonen: Neue potentielle DNA-Interkalatoren

1991

Diels-Alder reactions of 2- and 3-vinylindoles with aryne, 1,4-benzo- and 1,4-naphtho-quinone lead to new six-ring annellated carbazoles. Molecular modeling studies predict that the compounds with coplanar framework are able to intercalate with the B-DNA.

Synthesis of toxyloxanthone B

2014

A synthesis of the naturally occurring xanthone toxyloxanthone B is described, in which the key step is the regioselective addition of a methyl salicylate to a substituted benzyne, followed by cyclization of the intermediate aryl anion to form the xanthone, the regiochemistry of the aryne addition being confirmed by X-ray crystallography. Subsequent introduction of the pyran ring by [3,3]-rearrangement and deprotection completed the synthesis.

[pi]-strain-induced electrophilicity in small cycloalkynes: a dft analysis of the polar cycloaddition of cyclopentyne towards enol ethers

2006

Small cycloalkynes possess a π-strain-induced electrophilicity related to the bending of the C–Csp–Csp bond angle. For cyclopentyne and benzyne, the electrophilicity index defined in the context of density functional theory gives a coherent rationale for the reactivity of these cycloalkynes, which may act as electrophiles in polar cycloaddition reactions toward enol ethers. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Efficient Synthesis of (P-Chirogenic) o-Boronated Phosphines from sec-Phosphine Boranes

2015

An efficient synthesis of boronated phosphines with an o-phenylene-bridge prepared from sec-phosphine boranes and using benzyne chemistry is reported. Successive reactions of sec-phosphine boranes with n-BuLi and 1,2-dibromobenzene, and then with boron reagents, afford the o-boronatophenylphosphine derivatives in 71% yields. The use of P-chirogenic sec-phosphine boranes leads to the free boronated phosphines with retention of configuration at the P-center after decomplexation. The reaction of P-chirogenic o-boronatophenylphosphine with KHF2 affords the corresponding trifluoroborated phosphine with ee >98%.

A DFT Study of Inter- and Intramolecular Aryne Ene Reactions

2015

The molecular mechanisms of inter- and intramolecular aryne-ene reactions have been theoretically studied by DFT methods at the MPWB1K/6-311G(d,p) level. These reactions proceed through a one-step mechanism via nearly asynchronous transition states (TSs), in which the C–C single bond formation is slightly more advanced than the hydrogen transfer process. These ene reactions show very low activation enthalpies (<1 kcal/mol) and are strongly exothermic by more than 73 kcal/mol. An electron localisation function (ELF) topological analysis of the changes of electron density during these ene reactions indicates that the bonding changes are nonconcerted. ELF topological analysis of the electron d…

A DFT Analysis of the Strain-Induced Regioselective[2+2]Cycloaddition of Benzyne Possessing Fused Four-Membered Ring

2005

Stereoselective synthesis of o-bromo (or iodo)aryl P-chirogenic phosphines based on aryne chemistry.

2012

The efficient synthesis of chiral or achiral tertiary phosphines bearing an o-bromo (or iodo)aryl substituent is described. The key step of this synthesis is based on the reaction of a secondary phosphine borane with the 1,2-dibromo (or diiodo)arene, owing to the formation in situ of an aryne species in the presence of n-butyllithium. When P-chirogenic secondary phosphine boranes were used, the corresponding o-halogeno-arylphosphine boranes were obtained without racemization in moderate to good yields and with ee up to 99%. The stereochemistry of the reaction, with complete retention of the configuration at the P atom, has been established by X-ray structures of P-chirogenic o-halogenopheny…

New electrophilic reactions of 2,2′-bisindolyls with acid chlorides and carbodienophiles

1996

Some new acylation and cyclization reactions of 2,2′-bisindolyls 1, 2 are described. The product patterns constitute acyl derivatives 3, 4, 5 and an aldehyde 7, indolo[2,3-a]carbazoles 6, 14, 17, 19, 20 and cyclopentadiindoles 22 and 24. In the reaction with aryne or diazotated anthranilic acid, a 3-benzoylindole derivative 9 and phenylindolyl azo dye 10 are formed. N-methylmaleimide reacts with 2,2′-bisindolyl 2 via Michael type addition, dehydrogenation and cyclization to several functionalized or anellated indole derivatives 11, 12, 13 and 14, respectively.

Arynic species II

1986

Abstract o-Benzyne and its 4-methyl, 4-chloro and 4-bromo-derivatives were generated in the thermal decomposition of two new kinds of polymer-bound precursors: 1(2-carboxyaryl)triazenes and 2-carboxyaryl-sulphonates. New kinds of trapping polymers for these elusive species are also presented.

Formation of arynezirconocenes from substituted diaryl bis (t-butylcyclopentadienyl) zirconium: application to the synthesis of new functionalizedort…

1991

The para-substituted diphenylzirconocenes [(t-BuCp)2Zr(p-C6H4R)2; R = Br, NMe2] (A) were easily obtained from the reaction of the appropriate organolithium reagent with bis(t-butylcyclopentadienyl)zirconium dichloride. Elimination of bromobenzene or N,N-dimethylaminobenzene from A by slight heating led to arynezirconocenes into which were inserted two equivalents of elementary chalcogens. As a result dichalcogenated zirconacycles [(t-BuCp)2ZrY2C6H3R; Y = S, Se] (B) were obtained. Complexes B constitute useful potential synthons in organic synthesis and a large family of new functionalized dichalcogenated benzenic compounds was prepared by reacting electrophiles. The structure of complexes B…