NHC-catalyzed regiodivergent syntheses of difunctionalized 3-pyrazolidinones from α-bromoenal and monosubstituted hydrazine.

A formal [3 + 2] annulation of α-bromoenal with monosubstituted hydrazine could give 1,5 or 2,5-difunctionalized 3-pyrazolidinone regiodivergently by tuning the structure of the N-Heterocyclic Carbene (NHC) catalyst. Moderate to high yields, mild reaction conditions, good regioselectivity and potential biological significance of the final product have made this protocol attractive for the assembly of 3-pyrazolidinone.

N-Heterocyclic Carbene-Catalyzed [4 + 2] Cyclization of Saturated Carboxylic Acid with o-Quinone Methides through in Situ Activation: Enantioselective Synthesis of Dihydrocoumarins.

An N-heterocyclic carbene (NHC)-catalyzed formal [4 + 2] synthesis of dihydrocoumarins was realized from saturated carboxylic acids and o-quinone methides via an in situ activation strategy. This protocol results in excellent diastereoselectivity and enantioselectivity and good yields and uses readily available and inexpensive starting materials.

NHC-catalyzed [4 + 2] annulation of 2-bromo-2-enals with acylhydrazones: enantioselective synthesis of δ-lactams.

An asymmetric assembly of δ-lactams was realized via the NHC-catalyzed formal [4 + 2] annulation of acylhydrazones and 2-bromo-2-enals bearing γ-H. The advantages of this protocol include high enantioselectivity, good yields, mild reaction conditions and potential biological significance of the final products.

N-Heterocyclic carbene-triggered transition-metal-free synthesis of 2,3-disubstituted benzofuran derivatives.

An NHC-triggered, transition-metal-free strategy for the efficient synthesis of 2,3-disubstituted benzofuran derivatives in moderate to excellent yields from aryl or alkyl aldehydes and o-quinone methides has been developed. This method features mild reaction conditions, operational simplicity, broad substrate scope and convergent assembly.

An Enantioselective Assembly of Dihydropyranones through an NHC/LiCl-Mediated in situ Activation of α,ß-Unsaturated Carboxylic Acids.

A straightforward N-heterocyclic carbene (NHC)/LiCl-mediated synthesis of dihydropyranones from α,ß-unsaturated carboxylic acids and 1,3-dicarbonyl compounds was realized through the in situ activation strategy. The key advantages of this protocol include ready availability and high stability of starting materials, good yields, and excellent enantioselectivity.

Structure-activity relationship study on the binding of PBDEs with thyroxine transport proteins.

Molecular docking and three-dimensional quantitative structure-activity relationships (3D-QSAR) were used to develop models to predict binding affinity of polybrominated diphenyl ether (PBDE) compounds to the human transthyretin (TTR). Based on the molecular conformations derived from the molecular docking, predictive comparative molecular similarity indices analysis (CoMSIA) models were developed. The results of CoMSIA models were as follows: leave-one-out (LOO) cross-validated squared coefficient q² (LOO) = 0.827 (full model, for all 28 compounds); q² (LOO) = 0.752 (split model, for 22 compounds in the training set); leave-many-out (LMO) cross-validated squared coefficient q² (LMO, two groups) = 0.723 ± 0.100 (full model, for all 28 compounds); q² (LMO, five groups) = 0.795 ± 0.030 (full model, for all 28 compounds); and the predictive squared correlation coefficient r²(pred) = 0.928 (for six compounds in the test set). The developed CoMSIA models can be used to infer the activities of compounds with similar structural characteristics. In addition, the interaction mechanism between hydroxylated polybrominated diphenyl ethers (HO-PBDEs) and the TTR was explored. Hydrogen bonding with amino acid residues Asp74, Ala29, and Asn27 may be an important determinant for HO-PBDEs binding to TTR. Among them, forming hydrogen bonds with amino acid residues Asp74 might exert a more important function.

5-Amino-7-(3-chloro-phen-yl)-3,7-di-hydro-2H-thieno[3,2-b]pyran-6-carbo-nitrile 1,1-dioxide.

The title compound, C(14)H(11)ClN(2)O(3)S, with fused thiophene and pyran rings, was synthesized via the condensation of dihydro-thio-phen-3(2H)-one 1,1-dioxide and 2-(3-chloro-benz-yl-idene)malononitrile catalysed by triethyl-amine in ethanol. The thio-phene ring adopts an envelope conformation and the pyran ring is planar (r.m.s. deviation = 0.0067 Å). The dihedral angle between the pyran and phenyl rings is 80.8 (1)°. The crystal packing is stabilized by inter-molecular N-H⋯N and N-H⋯O hydrogen bonds in which the cyano N and sulphone O atoms, respectively, acting as acceptors.

Ethyl 7-(4-bromo-phen-yl)-5-trifluoro-methyl-4,7-dihydro-tetra-zolo[1,5-a]pyrimidine-6-carboxyl-ate.

In the title compound, C(14)H(11)BrF(3)N(5)O(2), the pyrimidine ring adopts a flattened envelope conformation with sp(3)-hybridized carbon as the flap [deviation = 0.177 (3) Å]. The dihedral angle between tetra-zole and bromo-phenyl rings is 84.3 (1)°. In the crystal, mol-ecules are linked into centrosymmetric dimers by pairs of N-H⋯N hydrogen bonds.

5'-Amino-2-oxo-2',3'-dihydro-spiro-[indoline-3,7'-thieno[3,2-b]pyran]-6'-carbonitrile 1',1'-dioxide.

In the title compound, C(15)H(11)N(3)O(4)S, the dihedral angle between the mean planes of the dihydro-indol-2-one (r.m.s. deviation = 0.015 Å) and dihydro-thieno[3,2-b]pyran (r.m.s. deviation = 0.011 Å) ring systems is 89.53 (3)°. The crytal packing is consolidated by inter-molecular N-H⋯O and N-H⋯N hydrogen bonds, which link the mol-ecules into a two-dimensional network into sheets lying parallel to (100).