tropine (Stranger)
06-01-03 18:38
No 437092
      NaBH4 to reduce 2-carbomethoxytropinone?  Bookmark   

I would think that NaBH4 would be more selective than LiAlH4, as it would leave the ester group completely alone?  Any comments?
06-04-03 07:22
No 437769
      Yes! A few to begin with...
(Rated as: good idea!)

No way Jose, LiAlH4 will reduce your stuff in all the wrong ways like convert your carboxylate to an alcohol. It is the wron reagent. I've made a bunch of 2-Carbomethoxy and it is produced in an aqueous solution for starters. I presume that you are working with Findlay's JOC synthesis from the mid 50's. I dont keep paperwork around but I can give you some practical experience. When you are done making the "2" by addition of amine, aldehyde, and mono-ester [ I presume you know what I'm talking about] toss a CHCl3 layer on top and slowly acidify with stirring or you will froth out of your container due to CO2 production from the decarboxylation. When you hit the correct pH after acidification, the monodecarboxylate methyl ester will be done and you will be left with a solution of of "2"hydrochloride. The chloroform will contain the contaminants so seperate and toss. Do this again and clean your aqueous solution of more contaminants. What I have found is that when you basify the aqueous 2, it likes to stay in water, i.e. water is a very good solvent because it will form a hydrate salt, if you will allow the terminology. You can exploit this with an aqueous NaBH4 reduction using a stabilized aqueous solution of the same which is readily available. Another fact is that the ketone from the aqueous solution of 2 is locked in "EXO" confirmation and MAY help in producing EXO alcohol. That little jewel was in the paper! Once the alcohol forms, the 2 analog becomes insoluble in water! That I know from experience because I once worked at a pharma company making analogs that hindered the euphoric effects. I would suggest a 1 Molar soln of the 2 at pH 10 with a dropwise addition of stabilized NaBH4, about 0.30 moles, in an ice bath to keep your temperatures low to around 20 C. Extract with Tolune and you will see the color go right into the solvent. Hope I have been of some help. Oh, By the way, the synthetic stuff we produced we nicknamed "Dope-a-cane" because it made a few subjects more delerious than euphoric, so good luck.