Palladium-catalyzed enantioselective carbonylation reactions

Carbonylation, one of the most powerful approaches to the preparation of carbonylated compounds, has received significant attention from researchers active in various fields. Indeed, impressive progress has been made on this subject over the past few decades. Among the various types of carbonylation reactions, asymmetric carbonylation is a straightforward methodology for constructing chiral compounds. Although rhodium-catalyzed enantioselective hydroformylations have been discussed in several elegant reviews, a general review on palladium-catalyzed asymmetric carbonylations is still missing. In this review, we summarize and discuss recent achievements in palladium-catalyzed asymmetric carbonylation reactions. Notably, this review’s contents are categorized by reaction type.

Thyroid blood profile in high-yielding dairy cows with different ovarian reactions to superovulatory treatment

The reaction of cow ovaries to superovulatory treatment significantly depends on the physiological state of the animal, primarily on its endocrine status. The available information indicates that thyroid hormones can affect the processes of ovarian folliculogenesis in cattle.Objective: To study the thyroid profile in the blood of high-yielding dairy cows in relation to the response of the ovaries to superovulatory treatment.Materials and methods. Thirty four cycles of superovulation stimulation in 16 Holstein cows were studied. After synchronization of the estrous cycle and superovulatory treatment, on the first day of insemination (Day 0), the number of follicles with a diameter of more than 5 mm was recorded in each ovary using an ultrasound scanner. Furthermore, on Day 0 and on the 7th day after insemination (Day 7), the blood was taken from the cows to analyze the content of sex steroids and thyroid hormones by ELISA. The ovarian reaction was assessed by the total number of detected follicles and was divided into 3 types: I – more than 12 follicles (strong), II – 8-12 follicles (moderate), III – less than 8 follicles (weak).Results. The content of sex steroid hormones in the blood of cows on Day 0 did not depend on the type of the ovarian response. By Day 7, the concentration of progesterone increased in most animals, but was 2.7-fold higher (P <0.01) in the case of the strong reaction (type I) than in the case of the weak reaction (type III). Conversely, the serum concentration of estradiol-17β decreased 1.1 times (P <0.05) in cows with the moderate ovarian response (type II). In animals with the type I reaction, the content of thyroxine (T4) in the blood declined 1.2 times (P <0.05) one week after insemination. During the study period, there was also a reduction in the concentration of total triiodothyronine (T3) and reverse T3 (rT3) in cows with ovarian responses of types I and II (1.1-1.3 times, P <0.01-0.05). Concurrently, on Day 0, the T3 content in the blood of individuals with the type II reaction was 1.2-fold higher (P <0.05) than in individuals with the type III reaction. Totally, a positive relationship was found between the concentration of estradiol-17β and the concentration of thyroid hormones: for T4 – in the case of the type II ovarian response (r = 0.44, P <0.05), for T3 – in the case of the type I and II responses ( r = 0.57-0.64, P <0.001-0.05), for rT3 – in the case of the type III response (r = 0.52, P <0.01).Conclusions. Thus, the content of triiodothyronine in the blood of high-yielding dairy cows on the day of insemination is associated with the ovarian response to superovulatory treatment. In addition, during one week after insemination, the state of the thyroid system and its relationship with the level of estradiol-17β in the blood differ with different reactions of the ovaries to the introduction of exogenous gonadotropic hormones.

An Unconditional Positivity-Preserving Difference Scheme for Models of Cancer Migration and Invasion

In this paper, we consider models of cancer migration and invasion, which consist of two nonlinear parabolic equations (one of the convection–diffusion reaction type and the other of the diffusion–reaction type) and an additional nonlinear ordinary differential equation. The unknowns represent concentrations or densities that cannot be negative. Widely used approximations, such as difference schemes, can produce negative solutions because of truncation errors and can become unstable. We propose a new difference scheme that guarantees the positivity of the numerical solution for arbitrary mesh step sizes. It has explicit and fast performance even for nonlinear reaction terms that consist of sums of positive and negative functions. The numerical examples illustrate the simplicity and efficiency of the method. A numerical simulation of a model of cancer migration is also discussed.

14 Electrochemistry in Natural Product Synthesis

The multistep synthesis of natural products has historically served as a useful and informative platform for showcasing the best, state-of-the-art synthetic methodologies and technologies. Over the last several decades, electrochemistry has proved itself to be a useful tool for conducting redox reactions. This is primarily due to its unique ability to selectively apply any oxidizing or reducing potential to a sufficiently conductive reaction solution. Electrochemical redox reactions are readily scaled and can be more sustainable than competing strategies based on conventional redox reagents. In this chapter, we summarize the examples where electrochemistry has been used in the synthesis of natural products. The chapter is organized by the reaction type of the electrochemical step and covers both oxidative and reductive reaction modes.

Phase Equilibria in the System CaO-SiO2-La2O3-Nb2O5 at 1400 °C

CaO-SiO2-La2O3-Nb2O5 system is of great significance for the pyrometallurgical utilization of Bayan Obo tailing resources. In the present work, the phase equilibrium of this quaternary system at 1400 °C was determined by a thermodynamic equilibrium experiment. On the basis of the recently determined CaO-La2O3-Nb2O5 phase diagram, some boundary surfaces of primary phase fields of CaO-SiO2-La2O3-Nb2O5 phase diagram were modified; then, the 1400 °C isothermal surface in the primary phase fields of SiO2, CaNb2O6, Ca2Nb2O7, and LaNbO4 was constructed, respectively. On this basis, CaO-SiO2-Nb2O5 pseudo-ternary phase diagrams with w(La2O3) = 5%, 10%, 15%, and 20% were determined, respectively. Considering the importance of equilibrium crystallization reaction type, we proposed a new rule named Tangent Line Rule to judge the univariant reaction type in the quaternary phase diagram. By applying Tangent Line Rule and Tangent Plane Rule previously proposed, some univariant and bivariant crystallization reaction types in the CaO-SiO2-La2O3- Nb2O5 phase diagram were determined, respectively. The current work can provide original data for the establishment of a thermodynamic database of Nb-bearing and REE-bearing slag system; the proposed Tangent Line Rule will promote the application of a spatial quaternary phase diagram.

Organic Sulfinic Acids and Salts in Visible Light-Induced Reactions

Sulfinic acids and their salts are a useful source of sulfur-containing structures. Photocatalysis of these compounds with visible light enables chemists to achieve various transformations under mild conditions. This review article summarizes visible light-induced reactions of sulfinic acids and their salts. This article is organized by reaction type and brief discussions on plausible reaction mechanisms for typical transformations are presented.