C–H amination/cyclocarbonylation of allene carbamates: a versatile platform for the synthesis of α,β-unsaturated γ-lactams

Grigg, Ronald; Schomaker, Jennifer M.; Timokhin, Vitaliy I.

doi:10.1016/j.tet.2011.03.026

Cited by 37 publications

(16 citation statements)

References 36 publications

(18 reference statements)

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“…Our previous work has already demonstrated the utility of allene bis-aziridination to 1,4-diazaspiro[2.2]pentanes (DASPs) 2 (Scheme 1) as a convenient scaffold to access vicinal diaminated synthetic motifs. 6 In this communication, we report a complementary reactivity that allows for the conversion of these reactive intermediates to 3 and stereotriads of the form 4 .…”

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Synthesis of 1,3-Diaminated Stereotriads via Rearrangement of 1,4-Diazaspiro[2.2]pentanes

2012

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The synthesis of 1,3-diaminated stereotriads via the bis-aziridination of allenes is reported. The reactive 1,4-diazaspiro[2.2]pentane intermediates undergo a mild Brønsted acid-promoted rearrangement to yield 1,3-diaminated ketones in good yields with excellent stereocontrol. Directed reduction of the ketone can be achieved to yield a C-N/C-O/C-N stereotriad in high dr. The ability to transfer the axial chirality of the substrates to the products allows for the facile preparation of enantioenriched stereotriads from allenes in two simple steps.

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Synthesis of 1,3-Diaminated Stereotriads via Rearrangement of 1,4-Diazaspiro[2.2]pentanes

2012

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“…1 In our previous studies, we have described the treatment of homoallenic carbamates 1 with tetra-bridged dirhodium(II) carboxylate complexes to promote formation of 2a and 2b as the major products. 1a-d However, good chemoselectivity was reliant on the specific substitution of the allene and the presence or absence of branching in the tether. 1e Competing C-H insertion to yield 3 was exacerbated when the allene was trisubstituted or branching in the tether between the allene and the nitrogen source was present.…”

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“…1a-d However, good chemoselectivity was reliant on the specific substitution of the allene and the presence or absence of branching in the tether. 1e Competing C-H insertion to yield 3 was exacerbated when the allene was trisubstituted or branching in the tether between the allene and the nitrogen source was present. 1e Efforts to improve chemoselectivity by tuning Rh-based catalysts via the ligand were disappointing.…”

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“…1e Competing C-H insertion to yield 3 was exacerbated when the allene was trisubstituted or branching in the tether between the allene and the nitrogen source was present. 1e Efforts to improve chemoselectivity by tuning Rh-based catalysts via the ligand were disappointing. Thus, we needed to identify another catalyst system capable of delivering predictable and superior selectivity for allene aziridination, independent of substrate structure.…”

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Chemoselective Allene Aziridination via Ag(I) Catalysis

Rigoli

Weatherly

et al. 2012

Org. Lett.

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Allene aziridination generates useful bicyclic methylene aziridine scaffolds that can be flexibly transformed into a range of stereochemically complex and densely functionalized amine-containing stereotriads. The scope of this chemistry has been limited by the poor chemoselectivity that often results when typical dinuclear Rh(II) catalysts are employed with homoallenic carbamates. Herein, Ag(I) catalysts that significantly improve the scope and yield of bicyclic methylene aziridines that can be prepared via allene aziridination are described.

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