T3P-Promoted Synthesis of a Series of 2-Aryl-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-ones and Their Activity against the Kinetoplastid Parasite Trypanosoma brucei

A series of fourteen 2-aryl-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-ones was prepared at room temperature by T3P-mediated cyclization of N-phenyl-C-aryl imines with thionicotinic acid, two difficult substrates. The reactions were operationally simple, did not require specialized equipment or anhydrous solvents, could be performed as either two or three component reactions, and gave moderate–good yields as high as 63%. This provides ready access to N-phenyl compounds in this family, which have been generally difficult to prepare. As part of the study, the first crystal structure of neutral thionicotinic acid is also reported, and showed the molecule to be in the form of the thione tautomer. Additionally, the synthesized compounds were tested against T. brucei, the causative agent of Human African Sleeping Sickness. Screening at 50 µM concentration showed that five of the compounds strongly inhibited growth and killed parasites.

Bulky 2,6-disubstituted aryl siloxanes and a disilanamine

The crystal structures of 5-bromo-1,3-di-tert-butyl-2-[(trimethylsilyl)oxy]benzene, C17H29BrOSi, (I), 1,3-di-tert-butyl-2-[(trimethylsilyl)oxy]benzene, C17H30OSi, (II), and N-(2,6-diisopropylphenyl)-1,1,1-trimethyl-N-(trimethylsilyl)silanamine, C18H35NSi2, (III), are reported. Compound (I) crystallizes in space group P21/c with Z′ = 1, (II) in Pnma with Z′ = 0.5 and (III) in Cmcm with Z′ = 0.25. Consequently, the molecules of (II) are constrained by m and those of (III) by m2m site symmetries. Despite this, both (I) and (II) are distorted towards mild boat conformations, as is typical of 2,6-di-tert-butyl-substituted phenyl compounds, reflecting the high local steric pressure of the flanking alkyl groups. Compound (III) by contrast is planar and symmetric, and this lack of distortion is compatible with the lower steric pressure of the flanking 2,6-diisopropyl substituents.

Oxidation of hydroxymethylpyrazines and hydroxylated phenyl compounds in a gas chromatography inlet

Large proportions of aldehydes were formed when hydroxymethylpyrazines, and benzyl- and cinnamyl alcohols were analysed by gas chromatography-mass spectrometry using a heated inlet with a used glass inlet liner.