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. 2017 Oct 19;73(42):6067-6079.
doi: 10.1016/j.tet.2017.08.052.

Exploring hydroamination-cycloaddition-fragmentation sequences to access polycyclicguanidines and vinyl-2-aminoimidazoles

Ki-Hyeok Kwon  1 , Anne V Edwards  1 , Miao Yang  1 , Ryan E Looper  1
Affiliations

Exploring hydroamination-cycloaddition-fragmentation sequences to access polycyclicguanidines and vinyl-2-aminoimidazoles

Ki-Hyeok Kwon et al. Tetrahedron. .

Abstract

The intramolecular hydroamination of a guanidine on an eneyne unit affords a guanidine-substituted diene capable of reacting with dienophiles. These substrates undergo [4+2]-cycloaddition reactions to generate a series of complex cyclic- and spirocyclic-guanidines. Select substrates can further undergo a ring opening-elimination cascade that ultimately reveals a vinyl-2-aminoimidazole. As such this cascade reaction may find application in the synthesis of oroidin-type natural products and their analogues.

Keywords: 2-aminoimidazoles; Alkaloids; Cycloaddition; Heterocycle; Hydroamination.

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Figures

Figure 1
Figure 1
Biogenesis of complex pyrrole-2-aminoimidazole alkaloids form simple precursors.
Scheme 1
Scheme 1
Applications of ene-ynes in the the guanidine hydroamination sequence.
Scheme 2
Scheme 2
6-endo-selective hydroamination / [4+2]-cycloaddition sequence to access polyclicguanidines.
Scheme 3
Scheme 3
Scope of the 6-endo-selective hydroamination / [4+2]-cycloaddition sequence.
Scheme 4
Scheme 4
5-exo-selective hydroamination / [4+2]-cycloaddition sequence.
Scheme 5
Scheme 5
5-exo-selective hydroamination / [4+2]-cycloaddition-fragmentation sequence.
Scheme 6
Scheme 6
Scope of the [4+2]-Cycloaddition-fragmentation sequence to access vinyl-2-aminoimidazoles.
Scheme 7
Scheme 7
[4+2]-Cycloaddition sequence with an acylnitroso-dienophile.
Scheme 8
Scheme 8
Hydroamination-Michael addition-[4+2]-cycloaddition sequence.
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