(Earnest Bee)
12-10-03 06:15
No 475925
(Rated as: excellent)
This matherial was originally posted to Russian Hyperlab: Post 475245 (Erny: "Восстановление 2,5-DiMeOP2NP на U-Ni-A", Russian HyperLab)
Catalyst preparation was based on ../rhodium /urushib
This is the most successful procedure for the reduction of nitropropenes on Urushibara nickel catalyst I have ever seen in my dreams, and, I guess, the last one: since a long while the only reducing agent I've dreamed about was LAH.
To a 100 ml rb flask, fitted with a mechanical stirrer and containing 10 g of zinc dust and 3 ml water there was added 3 g of NiCl2x6H2O (of a "chemically pure" grade, IMHO, it is not necessary, purity of zinc is more important), dissolved in 10 ml of water, and the stirring begun. A vigorous reaction took place and the contents of the flask almost ran over; after 15 minutes stirring was stopped and the reaction mass was diluted with tap water and transferred into a 500 ml rb flask, where it was washed several times with tap water and the last time - with distilled water. The precipitated nickel was a dark-gray solid that did not differed much in color from the original zinc dust, when wet. It was digested with 160 ml of 13% acetic acid for 5 min. Zinc dissolution in acetic acid was exothermic and was accompanied by a violent evolution of a hydrogen gas, at the end black catalyst raised to the surface of the solution. All was then filtered with suction on a Shott filter, washed with 200 ml of distilled water and with small amount of IPA. The filtrate had a greenish color.
The catalyst was then transferred to the 500 ml rb flask, while still wet, together with 100 ml of IPA. There was then added a solution of 0,2 g of 2,5-DiMeOP2NP in 15 ml of IPA (the resulting solution was VERY diluted, it is not a must), 1 g of thin aluminum foil and 3 ml conc. hydrochloric acid, the mechanical stirrer was fitted to the neck of the flask and the stirring begun. Reflux condenser was not used. Reaction of aluminum with HCl starts slowly but then accelerates, so that the temperature of the reaction mass rises to 60-70°C.
When almost all the aluminum had dissolved, another g was added together with 3 ml conc. HCl. All in all, 4 g of aluminum and 12 ml of HCl was added during 2,5 hours.
At the end of the reaction enough conc. sodium hydroxide soln. was added to the RM so that the layers could separate. The upper light-yellow IPA layer was decanted, the lower layer washed once with a small amount of IPA, the extracts were combined, and IPA was distilled off. The remaining orange oil was dissolved in petroleum ether from which the amine was acidified out with HCl. This gave 80 mg of 2,5-DMA hydrochloride (~38%) as a light-brown caramel-like substance that did not crystallized at once (it sometimes needs a week to do that, even in a purer state) and was successfully brominated.
