Preparation and reactions of new zincated nitrogen-containing heterocycles
A range of nitrogen-containing iodinated or in some cases brominated heterocycles were converted to the corresponding zincated heterocyclic derivatives by the direct insertion of zinc dust under mild conditions (25°C to 70°C, 1-3 h) in a solvent like THF or DMAC. This reaction was extended to the preparation of zincated nucleic acid bases and nucleosides. The reaction of these new zinc reagents toward various electrophiles with palladium (O) or copper(I) catalysis allows the preparation of a broad range of polyfunctional nitrogen-containing heterocycles.
Prasad, A. S. Bhanu,Stevenson, Thomas M.,Citineni, Janakiram Rao,Nyzam, Valerie,Knochel, Paul
p. 7237 - 7254
(2007/10/03)
Preparation of zinc organometallics derived from nucleosides and nucleic acid bases and Pd(0) catalyzed coupling with aryl iodides
5-Iodouracil and 6-iodopurine derivatives readily insert zinc dust (25°C or 70°C) in THF or DMAC affording zincated nucleic acid base derivatives which undergo efficient palladium catalyzed cross-coupling reactions with aryl iodides in good yields. This r
Stevenson, Thomas M.,Prasad, A. S. Bhanu,Citineni, Janakiram Rao,Knochel, Paul
p. 8375 - 8378
(2007/10/03)
Coupling of Diazopurines, a Curious Steric Effect in a Free Radical Reaction
The reaction of adenine derivatives with nitrite esters in the presence of arenes was examined and found to give 6-arylpurines in good (83percent) to poor (11percent) yield.The arylated products consisted only of the meta and para isomers; none of the anticipated ortho isomers were found.The predominance of meta- and para-substituted products is attributed to steric effects.The evidence that the reaction proceeds via a purine radical includes light stimulation, relative insensitivity to electronic factors, and the facile reaction of the purine intermediate with pyridine N-oxide.Photolysis of 6-iodo-9-benzylpurine in the presence of anisole gave the same mixture of 6-(m-methoxyphenyl)- and 6-(p-methoxyphenyl)purine as did diazotization, suggesting that both reactions involve the same purine radical.
McKenzie, Thomas C.,Epstein, Joseph W.
p. 4881 - 4884
(2007/10/02)
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