RESUMEN
A practical and efficient methodology for the construction of 3-alkylquinoxalinones through base promoted direct alkylation of quinoxalin-2(1H)-ones with phosphonium ylides as alkylating reagents under metal- and oxidant-free conditions was developed. Various 3-alkylquinoxalin-2(1H)-ones were easily obtained in good to excellent yields. Tentative mechanistic studies suggest that this reaction is likely to involve a nucleophilic addition-elimination process.
RESUMEN
Objectives: To observe the phenomenon of transient expansion of right heart during contrast-enhanced ultrasound (CEUS) by SonoVue?ultrasound contrast agent (UCA) in Chinese experimental mini-pig , and to explore the possible causes of this phenomenon. Methods: 24 healthy Chinese experimental mini-pigs were randomly divided into 3 groups according to the dose of injected contrast agent: 2 ml group (n=8), 1 ml group (n=8) and 0.5 ml group (n=8). Cardiac structure and function at baseline and during contrast procedure were determined by contrast-enhanced echocardiography. Pigs in each group received bolus contrast agent injection followed by 5ml saline flush with baseline concentration, 2, 4 and 6-fold serial dilutions, respectively. When the right heart enlargement appeared, stop the injection and next injection followed after the right heart returned its original size. The study protocols discontinued at the time when the right heart enlargement did not appear post injection. Results: In 2 ml group, the number of right heart enlargement with different injection concentrations was 7, 6, 4, 3, respectively; in 1 ml group, the number of right heart enlargement with different injection concentrations was 6, 5, 3, 1; in 0.5 ml group, the number of right heart enlargement with different injection concentrations was 5, 5, 2, and 0, respectively. Incidence of right heart enlargement decreased in proportion with lower contrast agent amount, and lower contrast concentration(P<0.001). The right heart enlargement phenomenon occurred at about (26±15) s after the injection and lasted for about (47±21) s. Conclusions:Transient expansion of right heart phenomenon is common by bolus injection of contrast agent during CEUS in the Chinese mini-pigs, which may be related to the injected concentration and dosage of the contrast agent, as well as the injection mode and animal species.