30567-86-3Relevant articles and documents
Synthesis of Spirobicyclic Pyrazoles by Intramolecular Dipolar Cycloadditions/[1s, 5s] Sigmatropic Rearrangements
Dimirjian, Christine A.,Casti?eira Reis, Marta,Balmond, Edward I.,Turman, Nolan C.,Rodriguez, Elys P.,Di Maso, Michael J.,Fettinger, James C.,Tantillo, Dean J.,Shaw, Jared T.
supporting information, p. 7209 - 7212 (2019/10/02)
The formation of fused pyrazoles via intramolecular 1,3-dipolar cycloadditions of diazo intermediates with pendant alkynes is described. A subsequent thermal [1s, 5s] sigmatropic shift of these pyrazole systems resulted in a ring contraction, forming spirocyclic pyrazoles. The limitations of this rearrangement were explored by changing the substituents on the nonmigrating aromatic ring and by using substrates lacking an aromatic linkage to the propargyl group.
(Chiral) lithium-(magnesium-)zinc and lithium-cobalt combinations as dual reagents for aromatic deproto-metalation and aryl transfer to aldehydes
Tilly, David,Snégaroff, Katia,Dayaker, Gandrath,Chevallier, Floris,Gros, Philippe C.,Mongin, Florence
supporting information, p. 8761 - 8766 (2012/11/07)
The deprotonating ability of mixed lithium-zinc or lithium-magnesium-zinc combinations containing amido and alkyl ligands in tetrahydrofuran were compared using anisole as substrate and iodine to quantitatively trap the formed arylmetal species. The results showed that the deprotonating ability is hampered if a Grignard reagent is employed to introduce the alkyl ligand, and is reduced when 2,2,6,6-tetramethylpiperidino ligands are replaced by less hindered/basic chiral amido or alkyls. Concerning the interception of the generated lithium-zinc aryl species by aldehydes, the presence of amido ligands leads to side reactions/lower yields, and no clear improvement was observed if lithium-magnesium-zinc aryl species are used. Racemic mixtures to very low enantioselectivities were noted when chiral amido ligands were incorporated in the composition of the bases. Still with enantioselective aryl transfer to aldehyde as purpose, the deprotonating ability of mixed lithium-cobalt combinations containing amido and alkyl ligands were compared using anisole as substrate and anisaldehyde to trap the formed arylmetal species. As before, the deprotonating ability is reduced when 2,2,6,6-tetramethylpiperidino ligands are replaced by less hindered/basic alkyls or chiral amido. The trapping step using aldehydes being in this case more efficient, even in the presence of amido ligands, the alcohols were obtained in higher yields. With recourse to a lower interception temperature, and using only bis[(R)-1-phenylethyl]amino as ligands, 32 and 22% yield, and 69 and 65% ee were obtained using, respectively, anisaldehyde and 3,4,5-trimethoxybenzaldehyde to intercept the metalated anisole.
Deprotonative metalation of substituted aromatics using mixed lithium-cobalt combinations
Dayaker, Gandrath,Chevallier, Floris,Gros, Philippe C.,Mongin, Florence
experimental part, p. 8904 - 8910 (2011/01/04)
The deprotonation of anisole was attempted using different homo- and heteroleptic TMP/Bu mixed lithium-cobalt combinations. Using iodine to intercept the metalated anisole, an optimization of the reaction conditions showed that in THF at room temperature 2 equiv of base were required to suppress the formation of the corresponding 2,2′-dimer. The origin of the dimer was not identified, but its formation was favored with allyl bromide as electrophile. The metalated anisole was efficiently trapped using iodine, anisaldehyde, and chlorodiphenylphosphine, and moderately employing benzophenone, and benzoyl chloride. 1,2-, 1,3-, and 1,4-dimethoxybenzene were similarly converted regioselectively to the corresponding iodides. It was observed that 2-methoxy- and 2,6-dimethoxypyridine were more prone to dimerization than the corresponding benzenes when treated similarly. Involving ethyl benzoate in the metalation-iodination sequence showed that the method was not suitable to functionalize substrates bearing reactive functions.
