10.1021/ja01640a072
The study investigates the kinetics of hydrogen exchange between phosphine (PH?) and water containing 3% deuterium. The researchers measured the rate of approach to equilibrium by tracking the uptake of deuterium in phosphine. They found that under conditions where diffusion from the gaseous to the liquid phase is not rate-determining, the fraction of exchange follows the McKay rate law. The study involved using various buffer solutions, including those with acids like mandelic, formic, benzoic, acetic, and trimethylacetic acids, to explore acid catalysis. For base catalysis, sodium carbonate-sodium bicarbonate, disodium phosphate-trisodium phosphate buffers, and unbuffered 0.01 M sodium hydroxide were used. The experiments revealed that the reaction is first order with respect to hydronium ion (H?O?) and hydroxyl ion (OH?) concentration, with rate constants of 3.6 liters/mole second and 0.40 liters/mole second at 27°C, respectively. The study also explored the effects of general acid and base catalysis, inert salt concentration, phosphine pressure, and temperature on the exchange rate. The results provided insights into the acid and base properties of phosphine in aqueous solution, with estimates of the base dissociation constant (KB) and acid dissociation constant (KA) of phosphine.
10.1021/ol2018278
The research aimed to develop a new efficient method for the direct alkenylation of chromones via a palladium(II)-catalyzed C—H functionalization reaction. This method represents a significant improvement over the existing two-step process, which involves the formation of 3-halochromone and a palladium(0)-catalyzed Heck coupling reaction. The researchers found that the use of pivalic acid with Cu(OAc)3/Ag2CO3 provided superior reactivity in the cross-coupling of chromones with alkene partners. This approach successfully afforded various 3-vinylchromone derivatives, which are important structures in many biologically active compounds and versatile synthetic building blocks. The study demonstrated that the combination of pivalic acid, Cu(OAc)3, and Ag2CO3 played a crucial role in enhancing the reactivity and yield of the desired products. The findings represent an unprecedented example of C—H functionalization of chromones and a significant advance in the field of organic synthesis.
10.1021/acs.orglett.8b00797
The study presents a novel method for synthesizing ortho-alkynylated arylalkylamines using Cbz-amide as a directing group and an Ir(III) complex as the catalyst. The researchers optimized the reaction conditions, finding that [Cp*Ir(III)Cl2]2, Cs2CO3, and pivalic acid in cyclohexane at 80 °C were most effective. They demonstrated that various Cbz-protected benzylamines and arylethylamines with different substituents could be alkynylated to produce the desired products in moderate to good yields. The study also included preliminary mechanistic investigations suggesting that the amide group serves as a coordination center to assist the Ir(III) complex in C?H activation. The findings highlight the potential of this Cbz-amide-promoted C?H functionalization for practical applications in organic synthesis.
C
C:Corrosive;
