PhI(OAc)2-mediated trifluoromethylthiolation/oxidative cyclization of ynamides.

A PhI(OAc)2-mediated trifluoromethylthiolation/oxidative cyclization of ynamides with the Shen reagent has been established herein, providing a facile access to CF3S-substituted oxazolidine-2,4-diones bearing a quaternary carbon center in 38-85% yields with chemoselectivities of up to 99/1.

Pd/Cu-Catalyzed tandem head-to-tail dimerization/cycloisomerization of terminal ynamides for the synthesis of 5-vinyloxazolones.

An attractive and novel methodology involving Pd/Cu-catalyzed tandem head-to-tail dimerization/cycloisomerization of terminal ynamides for the synthesis of 3,5-disubstituted oxazolones was developed. Under Pd(PPh3)2Cl2/CuI cooperative catalyzed reaction conditions, it provided efficient access to 5-vinyloxazolones with exceptional functional group tolerance and good chemoselectivity. The control experiments demonstrated that Pd(PPh3)2Cl2 serves a key role in the dimerization of terminal ynamides and shows low catalytic activity in the intramolecular cyclization. Moreover, the hetero-Diels-Alder reaction of product 5-vinyloxazolones was also described, which provided polycyclic oxazolones in good yield.

Highly regio- and stereoselective trans-iodofluorination of ynamides enabling the synthesis of (E)-α-fluoro-ß-iodoenamides.

A highly regio- and stereoselective trans-iodofluorination reaction of ynamides with NIS and Et3N·3HF has been achieved, affording (E)-α-fluoro-ß-iodoenamides in moderate to good yields. The reaction proceeds under mild reaction conditions and exhibits good functional group compatibility.

Generation of Oxazolidine-2,4-diones Bearing Sulfur-Substituted Quaternary Carbon Atoms by Oxothiolation/Cyclization of Ynamides.

A novel method for metal-free oxothiolation of ynamides to construct oxazolidine-2,4-diones bearing sulfur-substituted quaternary carbon atoms has been developed. It represents a rare C-O bond cleavage of ynamides, as well as a facile and tandem approach for the formation of C-O, C-S, and C-Cl bonds. This redox-neutral protocol can be applied to the synthesis of multisubstituted oxazolidine-2,4-diones with good chemoselectivity and good yields of isolated products under mild conditions.

(IPr)CuF-catalyzed α-site regiocontrolled trans-hydrofluorination of ynamides.

With Et3N·3HF as the fluorination reagent, (IPr)CuF-catalyzed α-site regiocontrolled trans-hydrofluorination of ynamides has been achieved, affording (Z)-α-fluoroenamides in moderate to excellent yields. It was interesting to note that the regioselectivity of the reaction is reversed to that observed in the (Ph3P)3CuF-catalyzed hydrofluorination of ynamides. Additionally, a variety of different ynamides including oxazolidinonyl-, imidazolyl-, and N-sulfonyl ynamides were suitable for the reaction system and the subsequent oxidation of the fluorinated products enables a convenient synthesis to α-fluoroimides.

Palladium-catalyzed intramolecular cyclization of ynamides: synthesis of 4-halo-oxazolones.

A mild and efficient methodology involving Pd(PPh3)4-catalyzed intramolecular cyclization of N-alkynyl alkyloxycarbamates with CuCl2 or CuBr2 for the synthesis of 4-halo-oxazolones was developed. This reaction exhibiting good functional tolerance provided a new, efficient, and rapid synthetic process to 4-halo-oxazolones. The resulting 4-halo-oxazolones can serve as great potential precursors for the 3,4,5-trisubstituted oxazolones via a Pd-catalyzed cross-coupling reaction.

Studies on copper(I)-catalyzed highly regio- and stereo-selective hydroboration of alkynamides.

The copper(I)-catalyzed hydroboration of alkynamides with B2pin2 afforded the alkenamide boronates in 66% to nearly quantitative yields with high regio- and stereo-selectivity. It was interesting to note that the regio-selectivity of the reaction is opposite to that observed in the carbometallation reaction of alkynamides, and the resulting alkenyl boronates provided access to α,ß-disubstituted (Z)-alkenamides through further elaboration.

1,4-Di-bromo-2,5-di-p-toluoyl-benzene.

In the title compound, C22H16Br2O2, which has approximate non-crystallographic inversion symmetry, the dihedral angles between the central ring and the pendant rings are 89.1 (4) and 82.4 (3)°; the dihedral angle between the pendant rings is 12.1 (4)°. In the crystal, the packing is influenced by van der Waals forces and no aromatic π-π stacking is observed.

Formation of α-chalcogenyl acrylamides through unprecedented chalcogen-mediated metal-free oxyfunctionalization of ynamides with DMSO as an oxidant.

A novel chalcogen-mediated oxyfunctionalization mode of ynamides for the synthesis of α-chalcogenyl acrylamides has been developed. Independent of metal catalysts, external oxidants and additives, this mild process afforded a range of structurally diverse α-chalcogenyl acrylamides, including α-selanyl acrylamides and α-tellanyl acrylamides. Interestingly, diverse ynamides tolerated in this approach gave different stereoselectivities.

Regioselective iodoamination of terminal ynamides for the synthesis of α-amino-ß,ß-diiodo-enamides.

A mild and efficient methodology involving the I2/TBHP-mediated intermolecular iodoamination of ynamides with amines for the synthesis of α-amino-ß,ß-diiodo-enamides was developed. This reaction provides the first intermolecular iodoamination of terminal alkynes to diiodo-enamines and can be easily applied to a wide range of substrates.

Cu(I)- or Ag(I)-Catalyzed Regio- and Stereocontrolled trans-Hydrofluorination of Ynamides.

With Et3N·3HF as the fluorinating reagent, a copper(I)- or silver(I)-catalyzed ß/α-site-regiocontrolled trans-hydrofluorination of alkynamides has been achieved, affording the corresponding fluoro enamides in moderate to nearly quantitative yields with high regio- and stereoselectivity, respectively. The reaction proceeds under mild reaction conditions and exhibits good functional group tolerance. Further, the deuterium-labeling experiment confirmed the existence of the alkenylcopper intermediate.

Controlled Synthesis of 1,3,5-Oxadiazin-2-ones and Oxazolones through Regioselective Iodocyclization of Ynamides.

Two efficient processes based on the iodocyclization of ynamides have been developed: (i) N-alkynyl tert-butyloxycarbamates were found to undergo a rare 6-exo-dig ring closure reaction affording 1,3,5-oxadiazin-2-ones by using acetonitrile as solvent; (ii) In the absence of acetonitrile, N-alkynyl tert-butyloxycarbamates could undergo 5-endo-dig cyclization providing oxazolones.

Highly selective and sensitive gold nanoparticle-based colorimetric assay for PO4³â» in aqueous solution.

A rapid, simple and real-time colorimetric assay for detecting phosphate anions (PO4(3-)) in aqueous solution was developed. The method was based on a novel functionalized gold nanoparticles (MPTP-Zn-AuNPs), which was synthesized by the ligand-exchange reaction of 4'-(4-mercaptophenyl)-2,2':6',2″-terpyridine zinc(II) complex (MPTP-Zn) with citrate-stabilized aqueous AuNPs. The strong coordination between MPTP-Zn-AuNPs and PO4(3-) anion gave rise to a color change from wine-red to blue-gray that was discernible by the naked eye and an easily measurable alteration in the absorption spectrum of the particles in aqueous solution. And the new technique exhibited the high selectivity for PO4(3-) over 11 other anions and could be used to determine PO4(3-) with a detection limit of 11 ppm.