2-(Trimethylsilyloxy)furan as a dianion equivalent: a two-step synthesis of functionalized spirocyclic butenolides.
[reaction: see text] The use of 2-(trimethylsilyloxy)furan derivatives as dianion equivalents leads to a general and connective spiroannulation protocol for the efficient preparation of spirocyclic butenolides.
Unexpected preparation of (Z)-chloromethyleneketals and their sulfur analogues by a novel three-component condensation.
A novel multicomponent condensation, leading to the rare (Z)-chloromethyleneketals and their sulfur analogues, has been discovered. The mechanism of this reaction has been studied in some detail and subsequent modifications were performed on the adducts, leading to unusual Umpolung transforms.
C-Nucleoside studies-15: Synthesis of 3-β-D-arabinofuranosylpyrazoles and the D-arabinofuranosyl analogue of formycin☆
Abstract A synthesis of 7-amino-3-(β -D-arabinofuranosyl)pyrazolo[ 4 3- d ]pyrimidine ( 13 ), the D-arabino analogue of formycin ( 1 ), from D-mannose is described. 1 -(2,4-Dinitrophenyl)-3-(penta- O -acetyl-D- manno -pentahydroxypentyl)pyrazole was converted into the 4-nitro-derivative 18 in 90% yield using trifluoroacetyl nitrate. In four steps 18 was transformed into the 3-β-D-arabinofuranosylpyrazole 12 which gave the N-nitro derivative 24 in two further stages. Cine -substitution of the N-nitro group in 24 by cyanide ion was followed by elaboration of the pyrimidine ring to give 13 . All the reactions proceeded with complete regio and stereoselectivity.