19 research outputs found
Sequential Deprotonation–Alkylation of Binaphthyloxy-Substituted Phosphonochalcogenoates: Chiral Tri- and Tetrasubstituted Carbon Centers Adjacent to a Phosphorus Atom
Sequential
deprotonation and alkylation of 1,1′-binaphthyloxy-substituted
phosphonoselenoates and phosphonates resulted in the diastereoselective
formation of chiral tri- and tetrasubstituted carbon centers adjacent
to a phosphorus atom
Sequential Deprotonation–Alkylation of Binaphthyloxy-Substituted Phosphonochalcogenoates: Chiral Tri- and Tetrasubstituted Carbon Centers Adjacent to a Phosphorus Atom
Sequential
deprotonation and alkylation of 1,1′-binaphthyloxy-substituted
phosphonoselenoates and phosphonates resulted in the diastereoselective
formation of chiral tri- and tetrasubstituted carbon centers adjacent
to a phosphorus atom
α‑Hydroxy and α‑Oxo Selenoamides: Synthesis via Nucleophilic Selenocarbamoylation of Carbonyl Compounds and Characterization
Carbonyl
compounds were added to selenocarbamoyllithiums to generate
α-hydroxy and α-oxo selenoamides. Their conformations
were determined by X-ray analyses. These compounds adopted conformations
that were almost identical to those of ordinary amides. Unlike the
consistency of the chemical shifts of the Cî—»Se groups of the
selenoamides in <sup>13</sup>C NMR spectra and the <sup>1</sup><i>J</i> coupling constants of the Cî—»Se groups, the substituents
far from the selenium atom influenced the chemical shifts in <sup>77</sup>Se NMR
Reaction of Selenoamide Dianions with Thio- and Selenoformamides Leading to the Formation of 5‑Aminoselenazoles: Photophysical and Electrochemical Properties
5-Amino-2-selenazolines
were synthesized by reacting selenoamide
dianions generated from secondary selenoamides and BuLi with tertiary
thio- and selenoformamides followed by treatment with iodine. The
resulting 5-amino-2-selenazolines were further oxidized with iodine
to give 5-aminoselenazoles in moderate to good yields. The general
tendencies in the <sup>77</sup>Se NMR spectra of the starting selenoamides,
5-amino-2-selenazolines, and 5-aminoselenazoles were determined. The
chemical shifts of these compounds were highly influenced by the skeletons
involving the selenium atom as well as the substituents on the carbon
atoms of each skeleton. The molecular structures of 5-aminoselenazoles
were clarified by X-ray analyses, and their electronic structures
were elucidated by DFT calculations. Finally, UV–vis and fluorescence
spectroscopy and cyclic voltammetry (CV) of 5-aminoselenazoles were
performed, and their properties are discussed in relation to the substituents
on the selenazole rings
Harnessing Chalcogen-bonding Interactions To Establish Conformational Control in Dirhodium(II) Paddlewheel Complexes
Novel well-defined D2-symmetric dirhodium(II) carboxylate complexes that bear axially chiral binaphthothiophene delta-amino acid derivatives have been developed. Conformational control was achieved through chalcogen-bonding interactions between sulfur and oxygen atoms in each ligand, providing well-defined and uniform asymmetric environments around the catalytically active Rh(II) centers. These structural properties render such complexes excellent catalysts for the inside-type asymmetric intramolecular C–H insertion into alpha-aryl-alpha-diazoacetates to yield a variety of cis- alpha, beta-diaryl gamma-lactones, as well as the corresponding trans-isomers through epimerization, in high diastereo- and enantioselectivities. Short total syntheses of the naturally occurring gamma-lactones cinnamomumolide, cinncassin A7, and cinnamomulactone were also accomplished using this conformationally controlled catalyst.<br /
One-Pot Preparation of (NH)-Phenanthridinones and Amide-Functionalized [7]Helicene-like Molecules from Biaryl Dicar-boxylic Acids
A one-pot transformation of biaryl dicarboxylic acids to (NH)-phenanthridinone derivatives based on a Curtius rearrangement and subsequent basic hydrolysis was developed. This method is also applicable for the preparation of optically active amide-functionalized [7]helicene-like molecules. Furthermore, aza[5]helicene derivatives with a phosphate moiety were isolated as a product of the Curtius rearrangement step in the case of substrates that bear chalcogen atoms. The stereostructures of these products, revealed by X-ray diffraction analysis, suggested that chalcogen-bonding and pnictogen-bonding interactions might contribute to their stabilization. The configurational stability of the helicene-like molecules and their chiroptical properties were further investigated
Synthesis and Photophysical Properties of 5‑<i>N</i>‑Arylamino-4-methylthiazoles Obtained from Direct C–H Arylations and Buchwald–Hartwig Aminations of 4‑Methylthiazole
5-<i>N</i>-Arylamino-4-methylthiazoles
were synthesized from commercially available 4-methylthiazole in three
consecutive steps: (i) direct Pd-catalyzed C–H arylations of
the thiazole, (ii) bromination, and (iii) Pd-catalyzed Buchwald–Hartwig
aminations. The resulting thiazoles showed the longest-wavelength
absorption maxima at 338–432 nm, and luminescence was observed
at 455–726 nm, whereby the latter depends predominantly on
the substituents at the 2-position of the thiazole core. The introduction
of electron-accepting groups, in particular a nitro group, induced
substantial bathochromic shifts of the fluorescence. Thiazoles containing
a 3,5-bisÂ(trifluoromethyl)Âphenyl group at the 2-position exhibited
purple to blue emission in the solid state. The energy levels of the
frontier molecular orbitals and the Kohn–Sham plots of the
5-<i>N</i>-arylamino-4-methylthiazoles were obtained from
DFT calculations at the B3LYP/6-31+GÂ(d,p) level of theory