Categories: N-H Bond Formation >
Cleavage of C-N bonds
A synergistic catalytic system based on Pd-C in the presence of 1,1,2-trichloroethane enabled the N-debenzylation of benzylamines to yield crystal amine hydrochlorides in practically quantitative yields.
C. Cheng, J. Sun, L. Xing, J. Xu, X. Wang, Y. Hu, J. Org. Chem., 2009, 74, 5671-5674.
Optically pure C2-symmetrical cyclic amines were efficiently synthesized from the corresponding diols obtained from an enantioselective borohydride reduction of diketones in the presence of a chiral β-ketoiminato cobalt(II) catalyst.
M. Sato, Y. Gunji, T. Ikeno, T. Yamada, Synthesis, 2004, 1434-1438.
A new one-pot method is described for the removal of O- and N-allyl protecting groups under oxidative conditions at near neutral pH. The allyl group undergoes hydroxylation and subsequent periodate scission of the vicinal diol. Repetition of this reaction sequence on the enol tautomer of the aldehyde intermediate releases the deprotected functional group.
P. I. Kitov, D. R. Bundle, Org. Lett., 2001, 3, 2835-2838.
Deprotection of allyl ethers, amines and esters to liberate hydroxyl, amino and acid groups is achieved under mild conditions. The reagent combination employed for this transformation is polymethylhydrosiloxane (PMHS), ZnCl2 and Pd(PPh3)4.
S. Chandrasekhar, R. Reddy, R. J. Rao, Tetrahedron, 2001, 57, 3435-3438.
A convenient one-step RhCl3-catalyzed deprotection of acyclic N-allyl amides is described. Reactions of RhCl3 with n-PrOH provide an active rhodium hydride species to catalyze isomerization of N-allyl amides to corresponding enamides and generate a crucial catalytic amount of HCl to convert the enamides to deallylated amides through N,O-acetal exchange.
M. J. Zacuto, F. Xu, J. Org. Chem., 2007, 72, 6298-6300.
The homoallyl moiety (hAllyl) can be used as a general protecting group for several functionalities. It can be chemoselectively removed via a sequential, one-pot cross-metathesis/elimination sequence.
B. H. Lipshutz, S. Ghorai, W. W. Y. Leong, J. Org. Chem., 2009, 74, 2854-2857.
The reaction of aliphatic and aromatic secondary and tertiary N-tritylamines with lithium powder and a catalytic amount of naphthalene led to reductive detritylation affording the corresponding amines in good yields. The trityl group could selectively be removed in the presence of an allyl or a benzyl group.
C. Behloul, D. Guijarro, M. Yus, Synthesis, 2004, 1274-1280.
A totally regioselective transformation of aromatic N-4-methoxyphenylaziridine 2-carboxamides into 2-aminoamides is promoted by active manganese (Mn*). α-Amino ketones can be readily obtained by reaction of morpholine-derived 2-aminoamides with organolithium compounds.
J. M. Concellón, H. Rodríguez-Solla, V. del Amo, P. Díaz, J. Org. Chem., 2010, 75, 2407-2410.
Palladium and Raney nickel catalyze the methanolysis of strongly complexed borane-amine adducts. The method is applicable to primary, secondary, tertiary, and aromatic amines, and the mildness of the reaction conditions allows preservation of otherwise labile functional groups.
M. Couturier, J. L. Tucker, B. M. Andresen, P. Dube, J. T. Negri, Org. Lett., 2001, 3, 465-467.
A highly enantioselective, catalytic three-component coupling of aldehydes, alkynes, and 4-piperidone hydrochloride hydrate affords the corresponding tertiary propargylamines in useful yields. A selective cleavage of the piperidone protecting group is possible using either ammonia/EtOH or a polymer-supported scavenger amine.
P. Aschwanden, C. R. J. Stephenson, E. M. Carreira, Org. Lett., 2006, 8, 2437-2440.
The bifunctional ferrocene FcCH2CO2H, with electron donor and acceptor moieties in the same molecule, has been shown to be advantageous for use as a catalyst in the N-demethylation of a number of tertiary N-methylamines such as codeine, thebaine, and oripavine. These substrates are readily N-demethylated under mild conditions, employing sub-stoichiometric amounts of the substituted ferrocene at ambient temperature.
G. B. Kok, P. J. Scammels, Synthesis, 2012, 44, 2587-2594.
A catalytic amount of tetrasodium 5,10,15,20-tetra(4-sulfophenyl)porphyrinatoiron(II) effected N-demethylation of N-oxide analogues of opiates to the corresponding N-nor semisynthetic opiate pharmaceuticals in excellent yields. The catalyst was readily removed and recycled.
Z. Dong, P. J. Scammels, J. Org. Chem., 2007, 72, 9881-9885.
A general and efficient method enables the synthesis of tertiary amides from readily available tertiary amines and anhydrides in the presence of FeCl2 as catalyst and tert-butyl hydroperoxide in water (T-Hydro) as oxidant. Mechanistic studies indicated that the in situ-generated α-amino peroxide of tertiary amine and iminium ion act as key intermediates.
Y. Li, L. Ma, F. Jia, Z. Li, J. Org. Chem., 2013, 78, 5638-5646.
Demethylation of N,N-dimethylanilines was carried out in various ionic liquids and acetonitrile as well as under solvent-free conditions. The reactivity dramatically depends on the employed solvent, with [bmim]Cl showing the best reactivity.
S. Imoria, H. Togo, Synlett, 2006, 2629-2632.