![]() However, Imming and coworkers reported that, for producing dibromoindigo 1 on a large scale, this procedure was not as practical as the original Baeyer-Drewsen indigo procedure. This procedure was later used by Voss and Gerlach and by Cooksey, who obtained 66% and 69% yields, respectively, of 1 from the benzaldehyde 8. In 1950, Harley-Mason, following the earlier work of Thiele, reported that the sodium salt of 2-nitro-1- o-nitrophenylethyl alcohol ( 18), obtained by the nitro-aldol condensation (Henry Reaction) of o-nitrobenzaldehyde ( 16) with nitromethane ( 17), gives a 90% yield of indigo ( 19) when treated with alkaline sodium dithionite solution ( Scheme 4). The final condensation of the benzaldehyde 8 with acetone in all these reported syntheses consistently gives yields of no more than about 50%. Recently, the procedure of Pinkney and Chalmers was improved by Imming and coworkers, who achieved an overall 10% yield of 1 from 10 ( Scheme 3). The chromic acid oxidation of 12 was subsequently used by Pinkney and Chalmers and by Torimoto and coworkers in their syntheses of Tyrian purple, and also by Keinan and coworkers. The latter method had previously been used to prepare o-nitrobenzaldehyde from o-nitrotoluene in two steps through the corresponding Diacetate. As an alternative to this reaction, Barber and Stickings found that oxidation of 12 with chromic acid in the presence of acetic anhydride was a more reliable method, although the yields were hardly better. ![]() Īn additional drawback of the above scheme is that even the modest yields of the benzaldehyde 8 obtained by reaction of 12 with alkyl nitrites could not be reproduced by later workers. However, despite these improvements, the reported overall yield of 1 based on the starting toluidine was only 5.5%. Benzaldehyde 8 was subsequently condensed with acetone in the usual way to give dibromoindigo 1. A modest improvement was achieved via a related scheme by Rottig, who used ethyl instead of amyl nitrite for the conversion of toluene 12 to oxime 13. ![]() This synthesis of 2 is indeed shorter, but at the expense of rather low yields. The latter is then oxidatively cleaved with ferric ammonium sulfate to give the desired aldehyde 8. The substituted toluene is then condensed with amyl nitrite to give the oxime 13. In the latter procedure, 10 is nitrated in concentrated sulfuric acid to give 4-amino-2-nitrotoluene ( 11) or its sulfate, which is then diazotized and converted to 4-bromo-2-nitrotoluene ( 12) in a Sandmeyer reaction or one of its variants. Thus, van der Lee prepared 8 in 4 steps from p-toluidine ( 10) ( Scheme 2). ![]() Subsequent syntheses were accordingly based on shorter methods for the preparation of this aldehyde. This original Sachs and Kempf route is clearly inconvenient, due to the lengthy preparation of the bromonitrobenzaldehyde 8. Interestingly, the yield of dibromoindigo in the final step was not reported. Under the reaction conditions, the hydroxyketone 9 spontaneously cyclizes and undergoes oxidative coupling, but it could be isolated using trisodium phosphate instead of NaOH in the Claisen condensation. The substituted benzaldehyde 8 was prepared, in five steps starting from 2,4-dinitrotoluene ( 2), in an overall yield of about 34%. Thus, the first synthesis of 1, reported in 1903 by Sachs and Kempf ( Scheme 1), was based on the Claisen condensation of 4-bromo-2-nitrobenzaldehyde ( 8) with acetone, in analogy to the Baeyer-Drewsen process for the manufacture of indigo. Nearly all known syntheses of 6,6′-dibromoindigo ( 1) are based on the oxidative coupling of a 6‑bromoindole derivative, which is usually generated in situ. The original synthesis and its elaborations * Once you complete the game with this ship it becomes worth 65535.2.1. Below is a complete shop summary and I also have episode maps and all the datacubes, cutscenes and ship descriptions that appear in the game. This will be an encyclopaedia of information related to playing Tyrian 2000.
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