5-Exo-dig aminocylization/hydroxyfluorination of propargylic carbamates
The unprecedented annulation/hydroxyfluorination of propargylic carbamates to give 4-fluoromethyl-4-hydroxy-oxazolidinones was investigated. The reaction was effectively promoted by NaHCO3 and/or silver catalysis. The peculiar behavior of propa
Convenient synthesis of 4-methylene-2-oxazolidinones and 4-methylenetetrahydro-1,3-oxazin-2-ones via transition-metal catalyzed intramolecular addition of nitrogen atom to actylenic triple bond
2-Propynyl tosylcarbamates 1 undergo cyclization smoothly by the catalysis of CuCl/Et3N or AgNCO/Et3N to furnish 4-methylene-2-oxazolidinones 2 in good yields. The similar cyclization of the N-acyl derivatives of 1 (PhCO, MeCO, EtOCO, etc.) is catalyzed effectively by AgNCO/t-BuOK. These reactions accommodate a variety of substituents at C1 and C3 of 2-propyn-1-ol and provide (Z)-2 as single stereoisomers. The scope of the cyclization of 3-butynyl carbamates is rather limited, and in general only N-tosyl derivatives of terminally unsubstituted 3-butyn-1-ols undergo cyclization to give 4-methylenetetrahydro-1,3-oxazin-2-ones in synthetically useful yields by the catalysis of AgNCO/Et3N or AgNCO/t-BuOK.
Tamaru,Kimura,Tanaka,Kure,Yoshida
p. 2838 - 2849
(2007/10/02)
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