ABSTRACT
Various functionalised 4-amino-2-(methylthio)quinolines are synthesised through triflic acid-mediated N-heteroannulation of α-functionalized-ß-anilino-ß-(methylthio)acrylonitriles for the first time. The N-heteroannulation process is highly chemoselective and has mild reaction conditions. However, this process fails in the absence of the ß-methylthio group in the acrylonitriles. In addition, a new double N-heteroannulation process is demonstrated to synthesise indolo[3,2-c]quinolines from non-heterocyclic precursors. Natural product isocryptolepine is synthesised in four steps from an acyclic precursor.
ABSTRACT
Paracetamol and a few other acetanilide derivatives are reported as a special class of diamagnetic Chemical Exchange Saturation Transfer (diaCEST) MRI contrast agents, that exhibit contrast only when the molecules form inter-molecular hydrogen bonding mediated molecular chains or sheets. Without the protection of the hydrogen bonding their contrast producing labile proton exchanges too quickly with the solvent to produce any appreciable contrast. Through a number of variable temperature experiments we demonstrate that under the conditions when the hydrogen bond network breaks and the high exchange returns back, the contrast drops quickly. The well-known analgesic drug paracetamol shows 12% contrast at a concentration of 15 mM at physiological conditions. With the proven safety track-record for human consumption and appreciable physiological contrast, paracetamol shows promise as a diaCEST agent for in vivo studies.
ABSTRACT
An unprecedented formation of a meso-fused ß-ß' carbaporphyrin dimer and its monomer with a keto group was described. These analogues were synthesized from carbatriphyrin(3.1.1.) by a metal assisted strategy using PtCl2 salt in a single step without any prefunctionalized precursors. Upon dimerization, the monomeric ligand with a dianionic core is transformed into a dimeric structure with unique trianionic cores.
ABSTRACT
A copper-catalysed intramolecular N-arylation of 5-aminopyrazoles is demonstrated for the first time. Highly substituted pyrazolo[3,4-b]indoles are synthesized. In particular, the indole core is decorated with halogens and alkyl and methoxy groups. Furthermore, a selective N-arylation of unsymmetrical diaryl bromide containing pyrazoles is exemplified, resulting in valuable pyrazolo[1,5-a]benzimidazoles.
ABSTRACT
A catalytic site selective intramolecular C-S bond forming reaction is demonstrated for the first time. The C-H bond functionalization of α-aryl-thioacetanilides was efficiently catalyzed by 2 mol% NiBr2, resulting in valuable 2-aminobenzo[b]thiophenes in moderate to good yields. Furthermore, the selective sp2 C-H bond functionalization over sp3 is exemplified.
ABSTRACT
Various functionalized 2-aminobenzo[b]thiophenes have been synthesized at room temperature by the Ullmann coupling reaction for the first time. The enantiospecific coupling reaction has been further demonstrated without loss of optical purity. The newly synthesized 2-anilino-3-cyano-benzo[b]thiophenes are transformed into 11-amino-benzothieno[2,3-b]quinolines in the presence of triflic acid.
ABSTRACT
A rapid construction of quinolone fused heterocycles from single S,N-acetal precursors via double heteroannulation is described. The base, radical and metal-mediated reactions can control the C-N, C-S and C-O bond formations of the S,N-acetal with high chemoselectivity.
ABSTRACT
Deuterium labeled aromatic and heteroaromatic compounds are synthesized in good to excellent yields with >98% deuterium purity via palladium catalyzed deuterodehalogenation reaction using commercially available and inexpensive reagents. Selective deuteration of bromoaniline is also demonstrated without H/D exchange in an amino N-H group.
ABSTRACT
Tetraarylpyrazoles are synthesized from commercially available materials in three steps and found to exhibit Aggregation Induced Emission Enhancement (AIEE) characteristics. Removing one aryl unit from tetraarylpyrazole leads to Aggregation Caused Quenching (ACQ), thus the number of aryl groups plays an important role in exploring such a phenomenon.
ABSTRACT
Domino carbocationic rearrangement of a number of substituted 3- and 2-indolylcyclopropyl ketones with an alpha-bis(methylthio)methylene group in the presence of various protic/Lewis acids yields a variety of products, mainly the pentaleno fused indoles and the carbazole derivatives.
ABSTRACT
[reaction: see text] Highly efficient and regioselective synthesis of 1-aryl-3,4-substituted/annulated-5-(methylthio)pyrazoles and 1-aryl-3-(methylthio)-4,5-substituted/annulated pyrazoles has been reported via cyclocondensation of arylhydrazines with either alpha-oxoketene dithioacetals or beta-oxodithioesters.
Subject(s)
Pyrazoles/chemical synthesis , Molecular Structure , Pyrazoles/chemistry , StereoisomerismABSTRACT
[Reaction: see text]. An efficient highly regioselective protocol for the synthesis of isomeric 1,3-diaryl (or 1-aryl-3-alkyl) and 1,5-diaryl (or 1-aryl-5-alkyl)-5 (or 3)-(N-cycloamino)pyrazoles has been reported by cyclocondensation of common alpha-oxoketene N,S-acetal precursors with arylhydrazines by variation of reaction conditions.
