Synthesis of 3-Aminotropones from N-Boc-Protected Furan-2-amine (=tert-Butyl Furan-2-ylcarbamate; Boc=(tert-Butoxy)carbonyl) by Cycloaddition Reactions and Subsequent Rearrangement
✍ Scribed by Ángel M. Montaña; Juan A. Barcia; Gabriele Kociok-Köhn; Mercè Font-Bardia; Xavier Solans
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- German
- Weight
- 402 KB
- Volume
- 91
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
The 3‐aminotropones (=3‐aminocyclohepta‐2,4,6‐trien‐1‐ones) 4 were prepared in two steps by i) a [4+3] cycloaddition reaction between a conveniently substituted α,α′‐dihalo ketone 1 and a furan‐2‐amine derivative 2 functionalized at C(2) by a protected amino group (→3), and ii) a base‐induced molecular rearrangement of the cycloadduct 3 via cleavage of the O‐bridge. A mechanism for the formation of 3‐aminotropones is proposed on the basis of the initial deprotonation of the [(tert‐butoxy)carbonyl]amino (BocNH) group of 3, followed by O‐bridge opening, an acid–base equilibrium, and finally an alkoxyaluminate elimination to afford the conjugated stable troponoid system (Scheme 7).