80326-68-7Relevant academic research and scientific papers
Activation of Exocyclic α-Positions of Azole N-Oxides by O-Silylation
Begtrup, Mikael,Vedso, Per
, p. 2555 - 2564 (2007/10/02)
Exocyclic α-positions at immonium ring carbon atoms of pyrazole and 1,2,3-triazole 1-oxides are selectively attacked in a one-pot sequence comprising silylation with iodotrimethylsilane, deprotonation with 1,2,2,6,6-pentamethylpiperidine and allylic substitution of the trimethylsilyloxy group with the iodide ions liberated by the silylation.In this way 3- and 5-iodomethylpyrazoles as well as 4-iodomethyl-1,2,3-triazoles are obtained in good yields.These may be useful for the preparation of heteroarylmethyl derivatives since the iodine atom can be displaced by even weak nucleophiles such as acetate ions.The side chain iodination is complementary to O-alkylation of the N-oxides followed by nucleophilic attack which preferentially takes place at ring carbon atoms.
On the Problem of Regioselectivity in the 1,3-Dipolar Cycloaddition Reaction of Munchnones and Sydnones with Acetylenic Dipolarophiles
Padwa, Albert,Burgess, Edward M.,Gingrich, Henry L.,Roush, David M.
, p. 786 - 791 (2007/10/02)
The 1,3-dipolar cycloaddition reaction of several unsymmetrically substituted munchnones and sydnones with methyl propiolate has been examined.The initially formed cycloadducts readily extrude carbon dioxide to produce five-membered heteroaromatic ring compounds.The reaction of sydnones with methyl propiolate produced a mixture of regioisomeric pyrazoles.The analogous cycloaddition reaction of munchnones with methyl propiolate proceeds with formation of mixtures of both possible regioisomeric pyrroles.The structural assignment of the isolated adducts is based on spectroscopic data.The distribution of products depends on the nature and location of the substituent groups present on the heterocyclic ring.The observed regioselectivity is discussed on the basis of MO-perturbation theory.
