A highly regioselective synthesis of valuable gem-difluorinated C-furanosides from unprotected aldoses via a debenzylative cycloetherification (DBCE) reaction induced by diethylaminosulfur trifluoride is descibed. The scope and limitations of this DBCE reaction are described using a series of commercially available pentoses and hexoses to afford, without selective protection/deprotection sequences, the corresponding gem-difluorinated C-furanosides in moderate to good yields.
Ther ing-opening of N-tert-butanesulfinylethynylaziridines with lithium tris(dimethylphenylsilyl)zincate is reported.T he reactionisdemonstrated to be both stereoselective and stereospecific and to proceed through an anti-S N 2' process.F urther deprotection of the nitrogen atom under mild conditions allows access to 4-amino-1-(dimethylphenylsilyl)alleneswith high yields and levels of stereoselectivity.
A convenient one-pot palladium-catalyzed cascade process for the preparation of both benzoxazoles and benzothiazoles has been developed. While these reactions proceed to give similar compounds the mechanisms governing the processes are different as are the experimental conditions employed.
4-Aminopropargylic acetates afford 4-amino-1-allenylsilanes upon reaction with the lithium (triorganosilyl)zincate (PhMe2Si)3ZnLi. The reaction is both stereoselective and stereospecific and proceeds through syn-silylzincation of the carbon–carbon triple bond followed by subsequent anti-β-elimination of the acetate group.
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