Search results for "nucleophilic"

2020

Electrophilic (het)arenes can undergo reactions with nucleophiles yielding π- or Meisenheimer (σ-) complexes or the products of the SNAr addition/elimination reactions. Such building blocks have only rarely been employed for the design of enzyme inhibitors. Herein, we demonstrate the combination of a peptidic recognition sequence with such electrophilic (het)arenes to generate highly active inhibitors of disease-relevant proteases. We further elucidate an unexpected mode of action for the trypanosomal protease rhodesain using NMR spectroscopy and mass spectrometry, enzyme kinetics and various types of simulations. After hydrolysis of an ester function in the recognition sequence of a weakly…

Regioselective substitution of 6,7-dichloroquinoline-5,8-dione: synthesis and X-ray crystal structure of 4a,10,11-triazabenzo[3,2-a]fluorene-5,6-dion…

2003

6,7-Dichloroquinoline-5,8-dione (1) was reacted with a number of 2-aminopyridine derivatives. Of the several possible products of this reaction, 4a,10,11-triazabenzo[3,2-a]fluorene-5,6-dione (6), produced by condensation and rearrangement, was obtained as the major product, and its structure was subsequently unambigously determined by X-ray crystallographic study. Ortho-quinones were produced via nucleophilic substitution at position C7, which was unexpected, considering that para-quinones were produced via C6 substitution in the reaction between compound 1 and ethyl acetoacetate in our previous work. Such unexpected nucleophilic substitution at C7 provides an effective, yet simple route, t…

Synthesis and cytotoxicity of 6,11-Dihydro-pyrido- and 6,11-Dihydro-benzo[2,3-b]phenazine-6,11-dione derivatives

2003

6,11-Dihydro-pyrido[2,3-b]phenazine-6,11-diones and 6,11-dihydro-benzo[2,3-b]phenazine-6,11-diones were synthesized from 6,7-dichloro-5,8-quinolinedione and 2,3-dichloro-1,4-naphthoquinone. The study on the cytotoxicity on these products revealed that the pyridophenazinediones, tetracyclic heteroquinone analogues with three nitrogen atoms exhibited a high cytotoxicity on several human tumor cell lines. Compound 9c and 9e showed in vitro antitumor activity comparable or superior to doxorubicin against the human ovarian tumor cells (SK-OV-3) and the human CNS cells (XF 498). The IC(50) value for compound 9e was 0.06 microM against the human CNS cells (XF 498), which was 2.6 times higher than …

Unique regioselectivity in the C(sp3)-H α-alkylation of amines: the benzoxazole moiety as a removable directing group.

2014

The benzoxazol-2-yl- substituent was found to act as a removable activating and directing group in the Ir-catalyzed alkylation of C(sp(3))-H bonds adjacent to nitrogen in secondary amines. It can be easily introduced by oxidative coupling or by an SNAr reaction, and it can be removed by hydroxide or by hydride reduction. For 1,2,3,4-tetrahydroisoquinolines, activation exclusively takes place in the 3-position. A variety of activated as well as unactivated terminal olefins are suitable reaction partners.

Herbizide, VI [1] kernfluorierte 2,4-dianilino-6-(dihexylamino)-1,3,5-triazine

1985

Zusammenfassung Auf dem Wege der nucleophilen Substitution der Chloratome in 2,4-Dichlor- 6-(dihexylamino)-1,3,5-triazin durch Anilin werden das 2,4-Dianilino-6-(dihexylamino)-1,3,5-triazin und durch fluorierte Amine die (Dihexylamino)- 1,3,5-triazine mit den folgenden Resten zuganglich: (2-Fluoranilino)-, (3-Fluoranilino)-, (4-Fluoranilino)-, (2,4-Difluoranilino)-, (2,5-Difluoranilino)- und (2,6-Difluoranilino)-. Zur Charakterisierung der neuen Verbindungen sind die IR-, 1 H-NMR- und Massenspektroskopie herangezogen worden. 2,4-Bis-(2,4-difluoranilino)-6-(dihexylamino)-1,3,5-triazin vermag insbesondere herbizide und antidiabetische Wirkungen auszuuben.

On the reaction of 3-bromo-2-nitrobenzo[b]thiophene with some ortho-substituted anilines: an analysis of the products of reaction and of their NMR an…

2003

Abstract The title reaction, carried out in DMF in the presence of triethylamine or potassium carbonate, has furnished the ‘expected’ 3-amino-2-nitrobenzo[ b ]thiophenes 2 o together with the ‘unexpected’ 2-amino-3-nitrobenzo[ b ]thiophenes 3 o , thus recalling the situation observed with other weak nucleophiles in the presence of non-nucleophilic bases. The effects (electronic as well as steric) of the ortho -substituent (OH, NH 2 , OMe, Me, Et, F, Cl and Br) on the course of the reaction have been investigated, determining their influence on yields and product ratios ( 2 o / 3 o ). An analysis of 13 C NMR and MS spectra of 2 o and 3 o has been carried out. Ab initio computations on 2 o f …

EPR spectroscopic characterization of persistent germyl-substituted Pb(III)- and Sn(III)-radicals.

2010

In this report we present the synthesis and the detailed electron paramagnetic resonance (EPR) spectroscopic characterization of novel trivalent lead- and tin-based radicals comprising sterically demanding germyl substituents. The investigated radicals are derived from the recently reported trihypersilyl-substituted tetryl radicals *PbHyp3 and *SnHyp3. The tetryl radicals *Pb(Ge(SiMe3)3)3 (8), *Pb(Ge(SiMe3)3)2Si(SiMe3)3 (9), *PbGe(SiMe3)3(Si(SiMe3)3)2 (10), and *Sn(Ge(SiMe3)3)3 (11) show substitution patterns derived from stepwise (9, 10) or complete (8, 11) substitution of hypersilyl groups (Hyp = Si(SiMe3)3) in *PbHyp3 and *SnHyp3 by homologous hypergermyl groups (Hge = Ge(SiMe3)3). They …

A new mechanism for internal nucleophilic substitution reactions

2018

A new mechanism for the classic internal nucleophilic substitution reactions SNi by means of computational studies in the gas-phase, DCM and acetonitrile is reported. Despite the importance of the SNi mechanism, since the mid-1990s this mechanism has remained unexplored. This study focused mainly on the comparison between the mechanisms postulated to date for the SNi reactions and a new mechanism suggested by us that fits better the experimental observations. This comparative study has been applied to the conversion of ethyl, neopentyl, isopropyl and tert-butyl chlorosulfites into the corresponding alkyl chlorides. This new mechanism occurs through two transition structures. For primary and…

Reactivity of the ansa-Bridged Metallocene Dichlorides [X(η5-C5H4)2]MCl2 (X = SiMe2, CMe2; M = Mo, W) toward Metallophosphide Anions [PPh2M‘(CO)x]- (…

1997

Two kinds of ansa derivatives, [SiMe2(η5-C5H4)2]MCl2 and [CMe2(η5-C5H4)2]MCl2 (M = Mo, W), are reacted with metallophosphide anions [PPh2M‘(CO)x]- (M‘ = Cr, Mo, W, x = 5; M‘ = Fe, x = 4). The silicon-bridged derivatives give the bimetallic systems [SiMe2(η5-C5H4)(η5-C5H3PPh2M‘(CO)x)]M(H)(Cl), which result from a regioselective substitution at the 3-position on the cyclopentadienyl ligand. In contrast, with the CMe2-bridged compounds, the substitution reaction occurs at the metallic center, giving μ-phosphido bimetallic complexes [CMe2(η5-C5H4)2]M(Cl)(μ-PPh2)M‘(CO)x. The solid-state structure of the bimetallic complex [CMe2(η5-C5H4)2]W(Cl)(μ-PPh2)Fe(CO)4 (7d) is reported.

Aromatic Nucleophilic Substitution (SNAr) of meso-Nitroporphyrin with Azide and Amines as an Alternative Metal Catalyst Free Synthetic Approach To Ob…

2014

International audience; Aromatic nucleophilic substitution reaction of the nitro group of meso-nitroporphyrins with azide and various amines was achieved and represents an alternative procedure to C-N coupling reactions usually needed to obtain such meso-N-substituted porphyrins in good yields.