Reduction converts indigo into "white indigo" (leuco-indigo).

Dow also developed a range of anthraquinone vat dyes and by 1938 the product line consisted of:

The chemical structures of the Dowanone anthraquinone derived vat dyes are illustrated below:

Dowanone Blue BCS was indanthrone, discovered by the German chemist Rene Bohn in 1901.

Microscale Chemistry - The microscale synthesis of indigo dye

In 1865 the German chemist Johann Friedrich Wilhelm Adolf von Baeyer began working with indigo.

Indigo: History and Synthesis | Dye | Filtration

The product would be made as a paste with an indigo concentration of 20 percent.

The synthesis began with aniline which was reacted with sodium bisulfite and sodium cyanide to form N-cyanomethylaniline.

Baeyer–Drewson indigo synthesis - Wikipedia

A broken thermometer sets the scene for a breakthrough in indigo research. In this example of serendipity at work, BASF scientists discover that mercury is an excellent catalyst in the manufacture of phthalic acid, a key precursor in the synthetic production of indigo. Economic industrial production of the precious blue dye seems a viable option at long last. Seventeen years of research later, it is finally ready for sale as “Indigo rein BASF” (English: Indigo Pure BASF). The synthetic indigo is sold worldwide, especially in China, where blue jackets dyed with indigo are traditional clothing and BASF has been active since 1885. Later, in the 1960s, indigo blue denim jeans are adopted by an entire generation and have become a basic wardrobe essential for many people all over the world today.

This route is highly useful for obtaining indigo and many of its derivatives on the lab-scale, but was impractical for industrial-scale synthesis.

German chemist Von Baeyer discovered how to synthesis Indigo.

This review showcases various coupling reagents which have been implemented specifically for large-scale amide synthesis via the condensation of an acid and amine, while highlighting the benefits and drawbacks of each reagent on an industrial scale.

First U.S. Producer of Synthetic Indigo - …

Find out more about this Nobel Prize topic in the new book by Carson J. Bruns, and Nobel Prize winner Sir J. Fraser Stoddart. Read the written by Makoto Fujita and Jean-Pierre Sauvage (2016 Chemistry Nobel Laureate). Read the preface

Many ways exist to prepare the important dye indigo

Ortega-Avilés [12] detail a variety of other techniques which can be used to determine the composition of a painting, in their case a work titled 'Virgin of Sorrows' (photo, right) which purported to be an 'ancient' piece. Raman and infra-red spectra were taken of the microsamples taken from the painting and the results analysed to determine both the compounds present and specific signatures which betray the origin of the dyes. Specific impurities and methods of binding to canvas fibres help to determine, using data from known samples, where the dyes used came from, when they were made, and which methods were used to extract or synthesise them. The authors found that the painting was elaborated during the middle of the 18th Century or the early third of the 19th Century.

indigo synthesis | Dye | Aldehyde

The German monopoly on dyestuff manufacture was finally broken.

A range of redder shade brominated indigos soon followed, including Midland Vat Blue R.

Biosynthesis of Indigo Dye by Newly Isolated …

This Graduate School offers a three-year PhD program in chemistry. Students from the Indian and German partner institutes will have the opportunity to accomplish a six-month student exchange program.

In dye: Vat dyeing …to a soluble, colourless form, leucoindigo

By the turn of the century, reserves of atmospherically fixed nitrogen – used as a crop fertilizer in the form of sodium nitrate – are running out. New sources of nitrogen are badly needed. After five years of research and development at BASF, Carl Bosch, building on a process by the Karlsruhe­-based chemist Fritz Haber, succeeds in converting atmospheric nitrogen on an industrial scale and manufacturing synthetic ammonia, which is used in turn to produce nitrogen fertilizers. The downside of the method shows itself in the First World War, when ammonia is converted into nitric acid and supplied to the explosives industry. Ammonia synthesis was developed to provide for the nutrition of billions of people – and continues to do so today.