38917-24-7Relevant academic research and scientific papers
Solvent-Controlled, Site-Selective N-Alkylation Reactions of Azolo-Fused Ring Heterocycles at N1-, N2-, and N3-Positions, Including Pyrazolo[3,4- d]pyrimidines, Purines, [1,2,3]Triazolo[4,5]pyridines, and Related Deaza-Compounds
Bookser, Brett C.,Weinhouse, Michael I.,Burns, Aaron C.,Valiere, Andrew N.,Valdez, Lino J.,Stanczak, Pawel,Na, Jim,Rheingold, Arnold L.,Moore, Curtis E.,Dyck, Brian
, p. 6334 - 6353 (2018/06/01)
Alkylation of 4-methoxy-1H-pyrazolo[3,4-d]pyrimidine (1b) with iodomethane in THF using NaHMDS as base selectively provided N2-methyl product 4-methoxy-2-methyl-2H-pyrazolo[3,4-d]pyrimidine (3b) in an 8/1 ratio over N1-methyl product (2b). Interestingly, conducting the reaction in DMSO reversed selectivity to provide a 4/1 ratio of N1/N2 methylated products. Crystal structures of product 3b with N1 and N7 coordinated to sodium indicated a potential role for the latter reinforcing the N2-selectivity. Limits of selectivity were tested with 26 heterocycles which revealed that N7 was a controlling element directing alkylations to favor N2 for pyrazolo- and N3 for imidazo- and triazolo-fused ring heterocycles when conducted in THF. Use of 1H-detected pulsed field gradient-stimulated echo (PFG-STE) NMR defined the molecular weights of ionic reactive complexes. This data and DFT charge distribution calculations suggest close ion pairs (CIPs) or tight ion pairs (TIPs) control alkylation selectivity in THF and solvent-separated ion pairs (SIPs) are the reactive species in DMSO.
Direct, Regioselective N-Alkylation of 1,3-Azoles
Chen, Shuai,Graceffa, Russell F.,Boezio, Alessandro A.
supporting information, p. 16 - 19 (2016/01/15)
Regioselective N-alkylation of 1,3-azoles is a valuable transformation. Organomagnesium reagents were discovered to be competent bases to affect regioselective alkylation of various 1,3-azoles. Counterintuitively, substitution selectively occurred at the more sterically hindered nitrogen atom. Numerous examples are provided, on varying 1,3-azole scaffolds, with yields ranging from 25 to 95%.
Regioselective and efficient synthesis of N 7-substituted adenines, guanines, and 6-mercaptopurines
Maryska, Michal,Chudikova, Nadezda,Kotek, Vladislav,Dvorak, Dalimil,Tobrman, Tomas
, p. 501 - 507 (2013/07/26)
A simple and efficient protocol for the preparation of N 7-substituted adenines, guanines, and 6-mercaptopurines is described. The key step is the regioselective preparation of 7-substituted 6-chloropurines which are building blocks for the div
PHOTOCHEMISTRY OF PURINE 3-OXIDES IN HYDROXYLIC SOLVENTS
Lam, Fuk L.,Parham, James C.
, p. 2371 - 2376 (2007/10/02)
UV irradiation of the potent oncogen hypoxanthine 3-oxide in aqueoous solution induces elimination of and rearrangement of the nitrogen-bound oxygen.The extent of each reaction shows a complex variation over the pH range 0-7.The variations in quantum yield for product formation are shown to result from the presence in the neutral molecule of tautomeric species with differing photochemistries that ionize in the excited state (pKa* ca. 3.5) just above the protonation pKa (1.2).The photochemical reactivity of each ionic and each tautomeric form was assigned by comparing the effect of pH changes between 0 and 11 on the quantum yields for formation of each photoproduct from hypoxanthine 3-oxide with those of two model compounds, 1-hydroxyhypoxanthine and 6-methoxypurine 3-oxide.Photoreduction of the 3-oxides occurs via the triplet state.This process has a relatively consistent low quantum yield (Φ=0.005 to 0.04) for most ionic and tautomeric forms of both purine 1-oxides and purine 3-oxides.Photorearrangement is a much more efficient process for purine 3-oxides (Φ=0.3) than for purine 1-oxides (Φ=0.04).
