Synthesis of Boronic Esters from Organometallic Reagents and Bis(pinacolato)diboron

Synthesis of alkyl, aryl, and vinyl boronic esters carrying various chiral and achiral diol-protecting groups were synthesized starting from the corresponding alkyl, aryl, and vinyl lithium or Grignard reagents. Good to excellent yields were obtained for a large range of substrates. The reaction can be conducted in a gram scale to obtain the product over 80 % yield. This approach provides direct access to neopentyl, pinene, and other boronic esters that are difficult to achieve. Using trimethoxyborane or 2-isopropoxy pinacolboronic ester. Detailed mechanistic studies have been conducted to understand the mechanism behind the formation of boronic ester starting from organometallic reagents.

Lipase-Assisted Synthesis of Alkyl Stearates: Optimization by Taguchi Design of Experiments and Application as Defoamers

The present work proposes the optimization of enzymatic synthesis of alkyl stearates using stearic acid, alkyl alcohols (C1-OH, C2-OH, C4-OH, C8-OH and C16-OH) and Candida rugosa lipase by a L9 (34) Taguchi-type design of experiments. Four variables were evaluated (reaction time, temperature, kU of lipase and alcohol:stearic acid molar ratio), ensuring that all variables were critical. In optimal conditions, five stearates were obtained with conversions > 90%. The obtained products were characterized by nuclear magnetic resonance (NMR). Additionally, the defoaming capacity of the five stearates was evaluated, obtaining better performance for the compound synthesized from C8-OH alcohol.

Ring Opening Reactions through C-O Bond Cleavage Uniquely Adding Chemical Functionality to Boron Subphthalocyanine

We are reporting the unexpected reaction between bromo-boron subphthalocyanine (Br-BsubPc) and THF, 1,4-dioxane or γ-butyrolactone that results in the ring opening of the solvent and its addition into the BsubPc moiety. Under heating, the endocyclic C-O bond of the solvent is cleaved and the corresponding bromoalkoxy-BsubPc derivative is obtained. These novel alkoxy-BsubPc derivatives have remaining alkyl-bromides suitable for further functionalization. The alkoxy-BsubPcs maintain the characteristic strongly absorption in visible spectrum and their fluorescence quantum yields.

Exchange of Alkyl and Tris(2-mercapto-1-t-butylimidazolyl)hydroborato Ligands Between Zinc, Cadmium and Mercury

The tris(2-mercaptoimidazolyl)hydroborato ligand, [Tm^But ], has been used to investigate the exchange of alkyl and sulfur donor ligands between the Group 12 metals, Zn, Cd and Hg. For example, [Tm^But ]₂Zn reacts with Me₂Zn to yield [Tm^But ]ZnMe, while [Tm^But ]CdMe is obtained readily upon reaction of [Tm^But ]₂Cd with Me₂Cd. Ligand exchange is also observed between different metal centers. For example, [Tm^But ]CdMe reacts with Me₂Zn to afford [Tm^But ]ZnMe and Me₂Cd. Likewise, [Tm^But ]HgMe reacts with Me₂Zn to afford [Tm^But ]ZnMe and Me₂Hg. However, whereas the [Tm^But ] ligand transfers from mercury to zinc in the methyl system, [Tm^But ]HgMe/Me₂Zn, transfer of the [Tm^But ] ligand from zinc to mercury is observed upon treatment of [Tm^But ]₂Zn with HgI₂ to afford [Tm^But ]HgI and [Tm^But ]ZnI. These observations demonstrate that the phenomenological preference for the [Tm^But ] ligand to bind one metal rather than another is strongly influenced by the nature of the co-ligands.

Structure-activity studies on nematicidal activity of dialkyl carbamates and thiocarbamates

In laboratory tests, 129 dialkyl carbamates of types ROC(O)NHR', RSC(O)NHR', and ROC(S)NHR' were tested in a screening bioassay against Panagrellus redivivus. The 10 most active were lethal at concentrations from 5 ppm down to ca. 1 ppm. Eight of these (the only ones active below 2.5 ppm) were thiolcarbamates (RSC(O)NHR'). Decyl N-methyhhiolcarbamate was also lethal to Meloidogyne incognita at approximately 1 ppm in direct contact tests.

Pentafluorophenyl Alkyl and Vinyl Ethers

The synthesis of various derivatives of pentafluorophenetole of the type C6F5OCH2CH2R is described. The R group was chlorine, bromine, hydroxyl, pentafluorophenoxy, acetoxy, and trifluoroacetoxy. 2-Pentafluorophenoxy-1,1,1-trifluoroethane and 1,1-bis(pentafluorophenoxy)ethane were similarly synthesized. A study was made of the behavior of these ethers toward pyrolysis, acids, and bases. In general, those ethers containing β-hydrogen atoms give pentafluorophenol on pyrolysis. Some compounds, such as 2-pentafluorophenoxyethyl bromide, give rearranged products as well. Under basic conditions, cleavage to pentafluorophenol was observed with aqueous potassium hydroxide, whereas the use of solid potassium hydroxide pellets gives dehydrohalogenated products. Concentrated sulfuric acid causes cleavage of most of the ethers employed. 2-Pentafluorophenoxy-1,1,1-trifluoroethane resists attack both by acids and bases. The synthesis and polymerization of two new vinyl monomers, pentafluorophenyl vinyl ether and 1,2-difluorovinyl pentafluorophenyl ether, are also presented.