Categories: C-O Bond Formation >
O-Derivatization of hydroxylamines, oximes and related compounds
A direct preparation of O-substituted hydroxylamines from alcohols is described by O-alkylation of tert-butyl N-hydroxyşcarbamate with the methanesulfonates of respective alcohols, followed by acidic N-deprotection.
S. Albrecht, A. Defoin, C. Tarnus, Synthesis, 2006, 1635-1638.
N-Hydroxyphthalimide and N-hydroxysuccinimide have been arylated with diaryliodonium salts to provide N-aryloxyimides in excellent yields in short reaction times. A mild and hydrazine-free hydrolysis gives aryloxyamines, which are valuable building blocks in the synthesis of oxime ethers and benzofurans.
R. Ghosh, B. Olofsson, Org. Lett., 2014, 16, 1830-1832.
An efficient Pd catalyst allows the O-arylation of ethyl acetohydroximate as an efficient hydroxylamine equivalent with aryl chlorides, bromides, and iodides. Short reaction times and broad substrate scope allow access to O-arylhydroxylamines that would be difficult to prepare. Moreover, the O-arylated products so formed can be directly transformed into substituted benzofurans in a single operation.
T. J. Maimone, S. L. Buchwald, J. Am. Chem. Soc., 2010, 132, 9990-9991.
Bench stable N-Methyl-O-alkoxyformate hydroxylamine hydrochloride reagents can be prepared in two high-yielding steps from N-Boc-N-methyl hydroxylşamine. Subsequent reaction with various carbonyl compounds give the corresponding α-functionalised products in good yield via a proposed [3,3]-sigmatropic rearrangement.
A. Hall, K. L. Jones, T. C. Jones, N. M. Killeen, R. P÷rzig, P. H. Taylor, S. C. Yau, N. C. O. Tomkinson, Synlett, 2006, 3435-3438.
The rate of the proline-catalyzed α-aminoxylation of aldehydes is significantly increased in the presence of a bifunctional urea originating from the hydrogen bonding interaction between the bifunctional urea and an oxazolidinone intermediate to increase the rate of enamine formation.
S. L. Poe, A. R. Bogdan, B. P. Mason, J. L. Steinbacher, S. M. Opalka, D. T. McQuade, J. Org. Chem., 2009, 74, 1574-1580.
An organocatalytic β-hydroxylation of α,β-unsaturated aldehydes with commercially available (E)-benzaldehyde oxime gives the corresponding chiral carbonyl β-oxime ethers in high yields and with excellent enantioselectivities. The chiral carbonyl β-oxime ethers can be reduced to the corresponding 1,3-diols in high yields.
S. Bertelsen, P. DinÚr, R. L. Johansen, K. A. J°rgensen, J. Am. Chem. Soc., 2007, 129, 1536-1537.
The oxygen atom of hydroxylamines having an N-electron-withdrawing substituent (also known as hydroxamic acids) acts as a reactive nucleophile in transition-metal-catalyzed allylic substitutions. The palladium-catalyzed O-allylic substitution of hydroxylamines with allylic carbonate afforded linear hydroxylamines, whereas branched hydroxylamines were observed in iridium-catalyzed reactions.
H. Miyabe, K. Yoshida, M. Yamauchi, Y. Takemoto, J. Org. Chem., 2005, 70, 2148-2153.
Treatment of alcohols with a mixture of triphenylphosphine, carbon tetrachloride, oxime, and DBU in the presence of catalytic amounts of tetrabutylammonium iodide in refluxing acetonitrile regioselectively furnishes the corresponding O-alkyl ethers in good yields.
M. N. S. Rad, A. A. Khalafi-Nezhad, F. Karimitabar, S. Behrouz, Synthesis, 2010, 1724-1730.
A facile esterification of ketoximes and aldoximes in high yields can be performed using N-[3-(methylamino)propyl]-N′-ethylcarbodiimide hydrochloride (EDCI) in the presence of 4-(dimethylamino)pyridine (DMAP) as a catalyst at room temperature. The isolation and purification is very simple and for solid products, column chromatography is avoided.
S. C. S. Kumar, N. V. Kumar, P. Srinivas, M. K. Bettadaiah, Synthesis, 2014, 46, 1847-1852.
A new reaction condition for Michael addition of oximes onto activated olefins has been discovered using a catalytic amount of triphenylphosphine. Various aldoximes and ketoximes were reacted with different Michael acceptors in good yields.
D. Bhuniya, S. Mohan, S. Narayanan, Synthesis, 2003, 1018-1024.
A copper-catalyzed cross-dehydrogenative coupling reaction between N-hydroxyphthalimide and aldehydes using PhI(OAc)2 as an oxidant enables a synthesis of NHPI esters in good yields in water. This facile and efficient method is eco-friendly and offers mild conditions, short reaction time, and broad substrate scope.
Z. Guo, X. Jiang, C. Jin, J. Zhou, B. Sun, W. Su, Synlett, 2017, 28, 1321-1326.