HCID 54074187, compound → HCID 86756084, compound

Participants

Reaction Steps

0.10 g of the oxindigo 1a (from Example 14) is dissolved in 40 ml of glacial acetic acid. 1.67 g (25.5 mmol) of zinc powder are introduced into the dark red solution. After the solution has been heated to the boiling point, it gradually becomes yellow in colour. The zinc sediment is filtered off to give a clear, dark yellow solution of blue fluorescence. A cotton ribbon is impregnated in this solution for 15 minutes. Chiefly the blue cis form 2a is then formed by oxidation in the air. During a couple of months in air and sunlight (during days) visually no color change is observed.

Provenance & Evidence