Baeyer–Drewson indigo synthesis - Wikipedia
The Baeyer-Drewson indigo synthesis (1882) isan in which is prepared from and
Baeyer-Drewson Indigo Synthesis | The Merck Index …
We recently unearthed a modification of the originalBaeyer-Drewson indigo synthesis. The first step of this reaction is a Henrytype reaction involving nitromethane conjugate base in place of the acetoneanion as nucleophile. The Henry reaction product is normally isolated (unlikethe aldol reaction product of the Bayer-Drewson reaction) and then trated withdithionite under basic conditions, followed by aerobic oxidative coupling togive indigo. Notably this procedure gives indigo in a much higher yieldscompared to the B-D reation (yields typically are ~10%).
The primary objectives and achievements to date havefocused on discovering and optimizing efficient synthetic routes toperi-naphthindigo (PNI) and its derivatives. We discovered thatBaeyer-Drewson type reaction of 8-nitro-1-naphthaldehyde with acetone underbasic conditions produced the parent PNI 1 in low yield (Scheme 1). Asanticipated, this molecule is an intensely absorbing green chromophore(absorption maximum 647 nm, extinction coefficient ~25,000). However, and nottotally unexpectedly, this flat species is quite insoluble in all commonsolvents.
Baeyer-Drewson indigo synthesis | SpringerLink
The Bayer-Drewson reaction to make PNI (this is thesame reaction used in the original synthesis of the famous pigment indigo,using ortho nitrobenzaldehyde in place of our nitro naphthaldehyde) clearly hasbecome a serious bottleneck to further progress. We decided to invest inexploration of a superior route to these compounds.
The Baeyer-Drewsen synthesis of indigo involves an interesting reaction series. Besides the incomplete and erroneous former attempts to explain the indigo formation process, there are recent contributions that are unsatisfactory from the theoretical point of view. Some are interesting but partially incorrect, others are incomplete and with stoichiometric errors, another is mere nonsense. We provide an up-dated and consistent reaction series, with comments on each step proposed by us, and also on those proposed by the others. These comments are based on well known reactions and reactivities. Since most names were lacking and others were unsuitable, not systematic or wrong, the appropriate nomenclature regarding the reaction intermediates is also given.
(2003) Baeyer-Drewson indigo synthesis.
Given its once economic significance, indigo has been prepared by many methods. The Baeyer-Drewson indigo synthesis dates back to 1882 but was impractical. The first practical route is credited to Pfleger in 1901. In this process, -phenylglycine is treated with a molten mixture of sodium hydroxide, potassium hydroxide, and sodamide. This highly sensitive melt produces indoxyl, which is subsequently oxidised in air to form indigo. Variations of this method are still in use today. An alternative and also viable route to indigo is credited to Heumann in 1897. It involves heating -(2-carboxyphenyl)glycine to 200 °C in an inert atmosphere with sodium hydroxide. The process is easier than the the Pfleger method but the precursors are more expensive. Indoxyl-2-carboxylic acid is generated. This material readily decarboxylates to give indoxyl, which oxidises in air to form indigo.
By 1897, 19,000 tons were produced from plant sources. Largely due to advances in organic chemistry, production by natural sources dropped to 1000 tons by 1914 and continued to contract. These advances can be traced to 1865 when the chemist Adolf von Baeyer began working with indigo. His work culminated in the first synthesis of indigo in 1878 (from istatine), a second synthesis in 1880 (from 2-nitrobenzaldehyde. The production of o-nitrobenzaldehyde was too complicated for a commercial product, so the search for alternative starting materials was crucial for BASF and Hoechst. The synthesis of N-(2-carboxyphenyl)glycine from the easy to obtain anthracene provided a new and economically attractive route. BASF developed a commercially feasible manufacturing process that was in use by 1897. In as of 2002[update], 17,000 tons of synthetic indigo were produced worldwide.
Baeyer–Drewson indigo synthesis
Baeyer-Drewson indigo synthesis
01/06/2016 · The Baeyer-Drewsen synthesis of indigo involves an interesting reaction series
Baeyer-Drewson indigo synthesis - ResearchGate
Full-text (PDF) | On the Mechanism of the Baeyer-Drewsen Synthesis of Indigo
Baeyer-Drewson Indigo Synthesis - DrugFuture
Baeyer-Drewson Indigo Synthesis
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