Catalytic Asymmetric Cycloadditions of Silyl Nitronates Bearing α-Aryl Group
摘要:
1,3-Dipolar cycloadditions of 2-alkylacroleins or atropaldehyde with triisopropylsilyl nitronates bearing an alpha-ary] group produced 3-aryl-2-isoxazolines having a chiral quaternary center in up to 94% ee and up to 88% yield with the aid of Corey's oxazaborolidine catalyst. Specifically, the TIPS nitronate with an alpha-(p-methoxyphenyl) group gave mainly the 2-isoxazolines having an all-carbon quaternary center.
2-Aryl-2-nitroacetates as Central Precursors to Aryl Nitromethanes, α-Ketoesters, and α-Amino Acids
摘要:
Nitroarylacetates are useful small molecular building blocks that act as precursors to alpha-ketoesters and aryl nitromethanes as well as alpha-amino acids. Methods were developed that produce each of these compound types in good yields. Two different conditions for decarboxylation are discussed for substrates with neutral and electron-poor aryl groups versus electron-rich aryl groups. For formation of the alpha-ketoesters, new mild conditions for the Nef disproportionation were identified.