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Synthesis of guanidines
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An efficient guanylation of various amines with cyanamide proceeds in the
presence of catalytic amounts of scandium(III) triflate under mild conditions in
water without using preactivated guanylation reagents. Therefore, the method has
practical utility for substrates that dissolve only in aqueous solutions, for
example, peptides or pharmacologically important compounds.
K. Tsubokura, T. Iwata, M. Taichi, A. Kurbangalieva, K. Fukase, Y. Nakao, K.
Tanaka,
Synlett, 2014, 25, 1302-1306.
Simple lanthanide amides are highly efficient catalysts for the guanylation of
both aromatic and secondary amines with a high activity under mild conditions.
These catalysts are compatible with a wide range of solvents and substrates.
Q. Li, S. Wang, S. Zhou, G. Yang, X. Zhu, Y. Liu, J. Org. Chem.,
2007,
72, 6763-6767.
Q. Li, S. Wang, S. Zhou, G. Yang, X. Zhu, Y. Liu, J. Org. Chem.,
2007,
72, 6763-6767.
Ytterbium triflate is an efficient catalyst for the addition of a wide scope of
amines to carbodiimides under solvent-free condition to provide N,N',N''-trisubstituted
guanidines in good yields.
X. Zhu, Z. Du, F. Xu, Q. Shen, J. Org. Chem., 2009,
74, 6347-6349.
Ru(bpy)3Cl2 as a photocatalyst enables the conversion
of various thioureas to the corresponding guanidines in a mixture of water and
ethanol at room temperature under irradiation by visible light. Key benefits of
this catalytic guanylation include the use low-toxicity solvents/base, ambient
temperature, and an open-flask environment.
T. Saetan, M. Sukwattanasinitt, S. Wacharasindhu,
Org. Lett., 2020, 22, 7864-7869.
An operationally simple and rapid copper-catalyzed three-component synthesis of
trisubstituted N-aryl guanidines involving cyanamides, arylboronic acids,
and amines is performed in the presence of K2CO3, a
catalytic amount of CuCl2·2H2O, bipyridine, and oxygen (1
atm).
J. Li, L. Neuville, Org. Lett., 2013,
15, 6124-6127.
An efficient Pd-catalyzed cascade reaction of azides with isonitriles and amines
provides N-sulfonyl-, N-phosphoryl-, and N-acyl-functionalized
guanidines in excellent yield. In addition, the less reactive intermediate
benzoyl carbodiimide could be isolated in moderate yield.
G. Qiao, Z. Zhang, B. Huang, L. Zhu, F. Xiao, Z. Zhang, Synthesis, 2018, 50,
330-340.
Carbamoyl isothiocyanates are ideal starting materials for the synthesis of
multisubstituted guanidines. The nature of these carbamoyl thioureas permits
creation of disubstituted and trisubstituted guanidines, as well as aromatic
guanidines.
B. R. Linton, A. J. Carr, B. P. Orner, A. D. Hamilton, J. Org. Chem., 2000,
65, 1566-1568.
Treatment of an acylcyanamide with chlorotrimethylsilane generates a reactive
N-silylcarbodiimide capable of guanylating a variety of amines. Typically
the reaction is complete in 15 min for primary and secondary aliphatic amines at
room temperature. Hindered amines and anilines are also competent nucleophiles
but require extended reaction times.
R. E. Looper, T. J. Haussener, J. B. C. Mack, J. Org. Chem., 2011,
76, 6967-6971.
The use of cyanuric chloride (TCT) instead of classical HgCl2 as
activating reagent for di-Boc-thiourea provides an alternative route for the
guanylation of amines and eliminates the environmental hazard of
heavy-metal waste without appreciable loss of yield or reactivity.
A. Porcheddu, L. De Luca, G. Giacomelli, Synlett, 2009,
3368-3372.
Two new guanidinylation reagents, N,N′-bis(ortho-chloro-Cbz)-S-methylisothiourea
and N,N′-bis(ortho-bromo-Cbz)-S-methylisothiourea,
proved to be superior to already known reagents. The guanidinylations of
amines with all reagents were accelerated by addition of DMAP.
T. Gers, D. Kunce, P. Markowski, J. Izdebski, Synthesis, 2004,
37-42.
A convenient one-step transformation of primary and secondary amines into
the corresponding unprotected guanidines using 4-benzyl-3,5-dimethyl-1H-pyrazole-1-carboxamidine
and its polymer-bound variant is described. The scopes and limitations of
the method, the microwave-assistance of amidination as well as a recycling
protocol are examined.
W. Solodenko, P. Bröker, J. Messinger, U. Schön, A. Kirschning,
Synthesis, 2006, 461-466.
A one-pot multicomponent carbonylation/amination sequence enables a convenient
synthesis of N-acylguanidines. A formation of an N-cyanobenzamide intermediate
from the Pd(0)-catalyzed carbonylative coupling of cyanamide and aryl iodides or
bromides is followed by amination with various amines to provide the final
N-acylguanidines in good yields. Furthermore, various heterocycles were prepared
from the N-acylguanidines.
L. Åkerbladh, L. S. Schembri, M. Larhed, L. R. Odell, J. Org. Chem.,
2017, 82, 12520-12529.
The synthesis of 3,5-dimethyl-N-nitro-1-pyrazole-1-carboxamidine (DMNPC) has been optimised. A detailed protocol for the preparation of a range of guanidines via nitroguanidines
is described using DMNPC as guanidinylating reagent.
J. A. Castillo-Meléndez, B. T. Golding, Synthesis,
2004,
1655-1663.
Primary amines are converted to protected NG-hydroxyguanidines
in a one-pot procedure using readily prepared materials. A high-yielding
preparation of NG-hydroxy-L-arginine, the intermediate in
the enzymatic conversion of L-arginine to nitric oxide and L-citrulline by
nitric oxide synthase, is described.
N. I. Martin, J. J. Woodward, M. A. Marletta, Org. Lett.,
2006, 8, 4035-4038.