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- Title
Dihydrooxazine Byproduct of a McMurry–Melton Reaction en Route to a Synthetic Bacteriochlorin.
- Authors
Tran, Vy-Phuong; Matsumoto, Nobuyuki; Nalaoh, Phattananawee; Jing, Haoyu; Chen, Chih-Yuan; Lindsey, Jonathan S.
- Abstract
A synthetic route to gem-dimethyl-substituted bacteriochlorins—models of native bacteriochlorophylls—relies on the formation of a dihydrodipyrrin precursor via a series of established reactions: van Leusen pyrrole formation, Vilsmeier formylation, Henry reaction, borohydride reduction, Michael addition, and McMurry–Melton pyrroline formation. The latter is the least known of the series. Here, the McMurry–Melton reaction of a 2-(6-oxo-2-nitrohexyl)pyrrole in the presence of TiCl3 and an ammonium acetate buffer formed the expected Δ1-pyrroline, as well as an unexpected polar, cyclic byproduct (a 5,6-dihydro-4H-1,2-oxazin-6-ol), each attached to the 2-methylpyrrole unit. Both species were characterized by single-crystal X-ray diffraction. The McMurry–Melton reaction is a type of intercepted Nef reaction (the transformation of a nitroalkyl motif into a carbonyl group), where both the Δ1-pyrroline and the dihydrooxazine derive from the reaction of the nitrogen derived from the nitro group upon complete or partial reductive deoxygenation, respectively, with the γ-keto group. The report also considers competing Nef and McMurry–Melton reactions, the nature of available TiCl3 reagents, and the use of ammonium acetate for buffering the TiCl3/HCl reagent.
- Subjects
AMMONIUM acetate; X-ray diffraction; PYRROLES; DEOXYGENATION; CHEMICAL reactions
- Publication
Organics, 2022, Vol 3, Issue 3, p262
- ISSN
2673-401X
- Publication type
Article
- DOI
10.3390/org3030019