Opportunities and Challenges for Construction Health and Safety Technologies under the COVID-19 Pandemic in Chinese Construction Projects.

The Coronavirus disease 2019 (COVID-19) pandemic has resulted in significant delays and cost overrun in construction projects. The implementation of health and safety (H&S) technologies is one of the most important strategies to alleviate the adverse impacts of COVID-19 on the construction industry and help the industry adapt to the new normal. This study aims to evaluate the adoption of H&S technologies for pandemic management in the construction sector under the COVID-19 pandemic.

Ligand-free iron-catalyzed benzylic C (sp)-H amination of methylarenes with -fluorobenzenesulfonimide.

Direct conversion of cheap methylarenes to benzylic amines, which are essential structural units of important drugs, is of great significance. However, the known methodologies suffer from the requirement of noble metal catalysts, heavy metal residues or strong oxidants. Herein, the first biocompatible iron-catalyzed benzylic C (sp)-H amination of methylarenes with -fluorobenzenesulfonimide is described.

(E)-N'-(3,4-Dichloro-benzyl-idene)nicotino-hydrazide monohydrate.

In the title compound, C(13)H(9)Cl(2)N(3)O·H(2)O, the 3,4-dichloro-benzene ring is nearly coplanar with the pyridine ring, making a dihedral angle of 4.78 (8)°. Inter-molecular O-H⋯O, O-H⋯N, N-H⋯O and weak C-H⋯O hydrogen bonding is present in the crystal structure.

N'-(Propan-2-yl-idene)nicotinohydrazide.

Crystals of the title compound, C(9)H(11)N(3)O, were obtained from a condensation reaction of nicotinohydrazide and acetone. In the mol-ecular structure, the pyridine ring is oriented at a dihedral angle of 36.28 (10)° with respect to the amide plane.

(E)-N'-(1,3-Benzodioxol-5-ylmethyl-ene)nicotinohydrazide monohydrate.

In the title compound, C(14)H(11)N(3)O(3)·H(2)O, the planar [maximum deviation 0.135 (1) Å] 1,3-benzodioxole ring system is oriented at a dihedral angle of 13.93 (7)° with respect to the pyridine ring.

N'-(3-Bromo-4-methoxy-benzyl-idene)nicotinohydrazide monohydrate.

In the title compound, C(14)H(12)BrN(3)O(2)·H(2)O, the benzene ring is oriented at a dihedral angle of 39.66 (11)° with respect to the pyridine ring. The solvent water mol-ecule links with the organic compound via O-H⋯O, O-H⋯N and N-H⋯O hydrogen bonding.

2,6-Dichloro-benzaldehyde oxime.

In the title compound, C(7)H(5)Cl(2)NO, there are two mol-ecules in the asymmetric unit. The mol-ecules are essentially identical. Each mol-ecule is connected to a symmetry-related mol-ecule through an inversion center by O-H⋯N hydrogen bonds, building an R(2) (2)(6) graph-set motif.

1-(4-Nitro-phen-yl)-2-(3-phenyl-allyl-idene)hydrazine.

In the title compound, C(15)H(13)N(3)O(2), the nitro-benzene and benzene rings make a dihedral angle of 9.1 (2)°. The crystal structure is consolidated by inter-molecular N-H⋯O hydrogen bonds.

2,4-Dichloro-benzaldehyde 2,4-dinitro-phenyl-hydrazone.

The asymmetric unit of the title compound, C(13)H(8)Cl(2)N(4)O(4), contains two independent but similar and almost planar mol-ecules. An intra-molecular N-H⋯O hydrogen bond is observed in each mol-ecule.

N'-(3-Phenyl-allyl-idene)isonicotino-hydrazide.

The asymmetric unit of the title compound, C(15)H(13)N(3)O, contains two similar mol-ecules. Each mol-ecule is non-planar, as indicated by the dihedral angles between the pyridine and benzene rings of 45.2 (2) and 56.

Synthesis of 1,1,4,4-tetrabromo-2-butenes and related compounds via desilylation-bromination of silylated 1,3-butadiene derivatives.

The combination of zirconocene-mediated coupling of silylated alkynes with a protonation-desilylation or bromination-desilylation process afforded otherwise unavailable butadiene derivatives. When (E,E)-2,3-dialkyl-1,4-bis(trimethylsilyl)-1,3-butadienes were treated with 3 equiv of Br(2) in CH(2)Cl(2), (E)-2,3-dialkyl-1,1,4,4-tetrabromo-2-butenes were obtained in excellent yields with perfect stereoselectivity.

Titanocene-catalyzed regioselective syn-hydrosilation of alkynes.

[reaction: see text] The titanium catalyst, which was generated in situ from titanocene dichloride and 2 equiv of butyllithium, was found to catalyze hydrosilation of a variety of alkynes with excellent regio- and syn-selectivity.