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Updated: Aug 19, 2026

Synthesis of 1,2-Azaborines and the Preparation of Their Protein Complexes with T4 Lysozyme Mutants
Published on: March 25, 2017
[Synthesis and spectral characterization of boron complexes of bis-schiff base from acylpyrazolone]
Jin-zhou Li1, Yu-mei An, Lu Wang
1Department of Chemistry, Harbin Normal University, Harbin, China.
Abstract:
Three novel bis-schiff base complexes [B(PMaFP)2en]Ac, [B(PMaFP)2pen]Ac and [B(PMTHP)2en]Ac have been synthesized, where (HPMalphaFP)2 en = N,N'-bis [(1-phenyl-3-methyl-5-oxo-4-pyrazolinyl) alpha-furylmethylidyne] ethylenediimine, (HPMalphaFP)2pen = N,N'-bis[(1-phenyl-3-methyl-5-oxo-4-pyrazolinyl) alpha-furylmethylidyne]-o-phenylenediimine and (HPMTHP)2en = N,N'-bis[(1-phenyl-3-methyl-5-oxo-4-pyrazolinyl)-2-thenoylmethylidyne] ethylenediimine. They were characterized by elemental analysis, IR, UV-Vis, 1H NMR, 13C NMR, and molar conductance measurements. The results show that the bis-schiff base is a quadridentate ligand and boron is four-coordinated in the complexes.
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Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
Acidity of 1-Alkynes
The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.
Hybridization of Atomic Orbitals I
Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration-Oxidation of Alkenes