Categories: C-N Bond Formation, Synthesis of cyclic amines >
Synthesis of aziridines
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Amino alcohols were converted into their hydrogen sulfates with chlorosulfonic
acid. The sulfates were cyclized with sodium hydroxide, and even with
non-nucleophilic sodium carbonate. This improved, mild variation of the typical
Wenker synthesis is applicable to unstable amino alcohols in hot sulfuric acid
and to unstable sulfates which favor elimination and hydroxide displacement in
the presence of strong base.
X. Li, N. Chen, J. Xu, Synthesis, 2010, 3423-3428.
Two alternative and complementary one-pot procedures for the direct
transformation of 2-amino alcohols to N-tosyl aziridines are presented. Less hindered
aziridines can be obtained in
high yields by tosylation and in situ cyclization effected by potassium
hydroxide in water/dichloromethane. Higher substituted amino alcohols give
better yields using potassium carbonate in acetonitrile.
L. W. Bieber, M. C. F. de Araujo, Molecules,
2002, 7, 902-906.
tert-Butyl hypoiodite is a mild and powerful reagent for the
cyclization of N-alkenylamides leading to various N-heterocycles.
N-alkenylsulfonamides gave three- to six-membered saturated N-heterocycles
in good yields, whereas alkenylbenzamide derivatives afforded
N-, O- or N-, S-heterocycles.
S. Minakata, Y. Morino, Y. Oderaotoshi, M. Komatsu, Org. Lett.,
2006,
8, 3335-3337.
Biologically important N-β-hydroxyethylaziridine intermediates were
conveniently prepared by regioselective ring-opening reactions of various
epoxides with in situ-generated ethyleneimine
from β-chloroethylamine under basic conditions in an aqueous environment.
H. Y. Kim, A. Talukdar, M. Cushman, Org. Lett.,
2006,
8, 1085-1087.
Vinylaziridines are useful and
versatile synthetic intermediates, as the relief of ring-strain provides a
driving force for efficient ring-opening or ring-expansion reactions.
Furthermore, the vinyl group can be derivatized into interesting
functionalities. The ring-closure of vicinal amino alcohols constitutes a
straightforward route to aziridines. Several methods exist for this
transformation, although many cannot be applied to vinylaziridines due to
their acid lability. This comparative study describes the most effective
sequences for the formation of N–H vinylaziridines.
B. Olofsson, R. Wijtmans, P. Somfai, Tetrahedron,
2002, 58, 5979-5982.
Reaction of N-(2-chloroethylidene)-tert-butylsulfinamide with
Grignard reagents or organoceriums gives terminal N-tert-butylsulfinyl
aziridines in good yields and with organoceriums good diastereomeric ratios.
Oxidation of terminal N-tert-butylsulfinyl aziridines provides
synthetically useful terminal N-Bus (Bus = tert-butylsulfonyl)
aziridines.
D. M. Hodgson, J. Kloesges, B. Evans, Synthesis, 2009,
1923-1932.
Related
N,N-Dialkyl-β-amino alcohols derived from α-amino acids can be
rearranged enantiospecifically by using TFAA/Et3N/NaOH to give 1,2-amino
alcohols.
T.-X. Métro, J. Appenzeller, D. G. Pardo, J. Cossy, Org. Lett.,
2006,
8, 3509-3512.
BH3 complexation of N-alkyl-2-phenylaziridines is able to
promote a regioselective β-lithiation. The lithiated intermediates were
configurationally stable, allowing an enantioselective preparation of cis-2,3-disubstituted
aziridines. The structure and stereochemistry of the synthesized BH3
complexes have been proved with DFT calculations and NMR experiments.
U. Azzena, G. Dettori, L. Pisano, B. Musio, R. Luisi, J. Org. Chem., 2011,
76, 2291-2295.
