Categories: C=N Bond Formation >
Synthesis of amidines
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Recent Literature
The condensation of primary amine with N,N-dimethylacetamide dimethyl
acetal yields a mixture of acetamidine and imidate ester depending on the
temperature, solvent, and structure of the primary amine. It is possible to
suppress the formation of imidate ester by performing the reaction in the
presence of excess dimethyl amine, yielding acetamidine as the exclusive product.
J. R. Harjani, C. Liang, P. G. Jessop, J. Org. Chem., 2011,
76, 1683-1691.
The reaction of enamines with azides proceeds under catalyst-free conditions and
results in the formation of either sulfonyl amidine or β-amino sulfonyl enamine
derivative in good yields.
T. Gao, M. Zhao, X. Meng, C. Li, B. Chen, Synlett, 2011,
1281-1284.
The addition of amines to nitriles catalyzed by ytterbium amides gives
monosubstituted N-arylamidinates in good to excellent yields at 100°C
under solvent-free conditions.
J. Wang, F. Xu, Q. Shen, Org. Lett., 2008,
10, 445-448.
A mild, metal-free, multicomponent reaction provides N-acyl amidines
from nitroalkene derivatives, dibromo amides, and amines via formation of an
initial α,α-dibromonitroalkane intermediate that can undergo C-C bond cleavage.
This alternative approach toward N-acyl amidines enables rapid
construction of amidine frameworks with high diversity and complexity.
M. Zhou, J. Li, C. Tian, X. Sun, X. Zhu, Y. Cheng, G. An, G. Li, J. Org. Chem., 2019, 84,
1015-1024.
NaI-catalyzed direct condensation of sulfonamides and formamides enables N-sulfonyl
formamidine synthesis without hazardous reagents or transition-metal catalysts.
The green methodology features high atom economy, operational simplicity, and
good tolerance with diverse functional groups.
S. Chen, Y. Xu, X. Wan, Org. Lett., 2011,
13, 6152-6155.
A silver-catalyzed, one-pot, four-component reaction of terminal alkynes,
TMSN3, sodium sulfinate, and sulfonyl azide provides amidines. A
possible cascade reaction mechanism consists of alkyne hydroazidation, sulfonyl
radical addition, 1,3-dipolar cycloaddition of TMSN3, and
retro-1,3-dipolar cycloaddition.
B. Liu, Y. Ning, M. Virelli, G. Zanoni, E. A. Anderson, X. Bi, J. Am. Chem. Soc.,
2019,
141, 1593-1598.
Cu-catalyzed aerobic oxidative three-component coupling of a terminal alkyne,
secondary amine, and sulfonamide enables an efficient synthesis of amidines. The
use of Cu(OTf)2 as catalyst produces amidines selectively via an
initial oxidative coupling of the terminal alkyne with the secondary amine,
followed by hydroamidation of the ynamine intermediate with the sulfonamide.
Glaser-Hay alkyne homocoupling products are not observed.
J. Kim, S. S. Stahl, J. Org. Chem.,
2015,
80, 2448-2454.
A highly efficient, mild, copper-catalyzed multicomponent reaction
for the synthesis of N-sulfonylamidines has been developed. This reaction has an
extremely wide scope with regard to all three coupling components of alkyne,
sulfonyl azide, and amine. Two plausible mechanistic pathways are discussed.
I. Bae, H. Han, S. Chang, J. Am. Chem. Soc.,
2005, 127, 2038-2039.
Yb(OTf)3 catalyzes a regioselective hydroamination of ynamides with
anilines and p-toluenesulfonamide to provide a diverse range of amidines
with good functional group tolerance in good yields.
X. Zeng, Q. Gu, W. Dai, Y. Xie, X. Liu, G. Wu, Synthesis, 2021, 53,
2889-2896.
Related
Amidines can be prepared
by reducing acylated amidoximes with potassium formate. This method has
proved to be very simple and effective.
K. Nadrah, M. Sollner Dolenc, Synlett, 2007,
1257-1258.