Versuche zur Redox-Simulation der photochemischen A/D-Secocorrin → Corrin-Cycloisomerisierung. Elektrochemische Oxydation von Nickel(II)-1-methyliden-2,2,7,7,12,12-hexamethyl-15-cyan-1,19-secocorinat-perchlorat. Vorläufige Mitteilung
✍ Scribed by Bernhard Kräutler; Andreas Pfaltz; René Nordmann; Keith O. Hodgson; Jack D. Dunitz; Albert Eschenmoser
- Publisher
- John Wiley and Sons
- Year
- 1976
- Tongue
- German
- Weight
- 897 KB
- Volume
- 59
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Experiments on a simulation of the photochemical A/D‐secocorrin → corrin cycloisomerization by redox processes. Electrochemical oxidation of nickel(II)‐1‐methylidene‐2,2,7,7,12,12‐hexamethyl‐15‐cyano‐1,19‐secocorrinate perchlorate
Can the act of light excitation in the photochemical A/D‐secocorrin → corrin cycloisomerization be replaced by redox reactions in the dark? Electrochemical oxidation of nickel(II)‐A/D‐secocorrinate 4 in acetonitrile containing a trace of water produces the secocorrinoxide–nickel‐complex 5 (structure determined by X‐ray analysis) in almost quantitative yield. This two‐electron oxidation involves a hydrogen shift from the methylene group C(19) in ring D to the methylidene carbon atom at ring A in the radical cation intermediate. Since the same type of hydrogen shift occurs in the photochemical A/D‐secocorrin → corrin cycloisomerization, a close parallelism in their chemical reactivity seems to exist between electronically excited A/D‐secocorrins and corresponding radical cations. Formation of the corrin complex 2 (M = Ni^+^) could be achieved (so far only in modest yields) by electrochemical one‐electron oxidation of 4 in acetonitrile/acetanhydride/acetic acid 8:1:1 followed by one‐electron reduction. – The transformation of the oxide nickel complex 5 to the corrinoid complex 10 – a new member in the family of dehydrocorrins – is also recorded.