RESUMO
A nucleophilic addition/ring-contractive rearrangement of α-bromo N-alkoxylactams with organometallic reagents was developed, providing an efficient access to α-acylpyrrolidines incorporating various C(sp2) units such as aryl, heteroaryl, and alkenyl groups. The sequential reaction proceeds through a five-membered chelate formation using nucleophilic addition followed by ring contraction via the formation of N,O-hemiaminal with good yields and a broad substrate scope. Moreover, a preliminary result with the use of the chiral N-alkoxylactam for the diastereoselective reaction is described.
RESUMO
Glasses with high elastic moduli have been in demand for many years because the thickness of such glasses can be reduced while maintaining its strength. Moreover, thinner and lighter glasses are desired for the fabrication of windows in buildings and cars, cover glasses for smart-phones and substrates in Thin-Film Transistor (TFT) displays. In this work, we report a 54Al2O3-46Ta2O5 glass fabricated by aerodynamic levitation which possesses one of the highest elastic moduli and hardness for oxide glasses also displaying excellent optical properties. The glass was colorless and transparent in the visible region, and its refractive index nd was as high as 1.94. The measured Young's modulus and Vickers hardness were 158.3 GPa and 9.1 GPa, respectively, which are comparable to the previously reported highest values for oxide glasses. Analysis made using (27)Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy revealed the presence of a significantly large fraction of high-coordinated Al in addition to four-coordinated Al in the glass. The high elastic modulus and hardness are attributed to both the large cationic field strength of Ta(5+) ions and the large dissociation energies per unit volume of Al2O3 and Ta2O5.
