tropine
(Stranger) 07-11-03 01:00 No 446280 |
Findlay's 2=carbomethoxytropinone article | |||||||
Thsi article seems to have a glaring error where he uses LiAlH4 to reduce the 2-carbomethoxytropinone to produce the hydroxy group from the ketone carbonyl. Not only would that carbonyl be reduced, but the ester carbonyl would also be reduced yeild a whole host of crap. Why wouldn't he use the obvious NaBH4? The only reason I can think of is the LiAlH4 would preferentially reduce the ketone carbonyl first, this would consume all of the LiAlH4 and there would be none left to react with the ester carbonyl. But this sounds like sledgehammer chemistry, it is possible that the other reason is that NaBH4 forms the incorrect isomer? |
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slappy (Hive Addict) 07-13-03 13:54 No 446796 |
Yes | |||||||
LAH always delivers hydride axially. And in this case, you are going to want the equtorial alcohol. And, if LAH is used in stoichiometric amounts will reduce ketone only. The k(C=O->CH-OLi)/k(CO2Me->CH-OLi+MeO |
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politoxicomania (Stranger) 09-09-03 22:48 No 457965 |
NaBH4 | |||||||
yes one can use every H producing agent but for ketons NaBH4 is the most selective one the problem ist that hydroxy group will be 80% the wrong position thats the reason why still natriumamalgan is used the refs given from rhodium are excellent the problem ist that these refs are about reducing the tropinone reducing the 2-carbomethoxy-tropinone will have possible cyclic intermediates which changes the stereochemistry of the reduction where are the refs about that ? |
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Rhodium (Chief Bee) 09-10-03 04:31 No 458047 |
Stereochemistry of the Reduction of Tropinone (Rated as: excellent) |
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This is not a chatroom! Think before you post, and if you still feel you need to add something more (or correct an error), use the Edit button, don't make an extra post. Why don't you post some selective reduction methods with references which are better than the procedures from my page which you trashed in another post of yours, instead of just writing small non-informative comments here and there? Stereochemistry of the Reduction of Tropinone to Tropine/Pseudotropine I'll begin with posting two landmark articles on the stereoselective reduction of tropinone in high yield, the ratios between tropine/pseudotropine being anything from 2:1 to 1:9 depending on the reaction conditions. Over three dozen reducing systems were evaluated, including NaBH4/LiBH4/KBH4 (in water or alcohols), LiAlH4 (in ether or THF), Sodium in toluene or alcohols, and Al(i-PrO)3 in i-PrOH. They also equilibrate either tropine or pseudotropine using either of the two latter (reversible) systems, and measure where the equilibrium point between the alcohols lie in different solvent systems. Reduction of Tropinone A. H. Beckett et. al. Chemistry and Industry, p. 663 (1957) (../rhodium/djvu /tropinone.r Stereochemistry of the Reduction of Tropinone A. H. Beckett et. al. Tetrahedron, Vol. 6, pp. 319-330 (1959) (../rhodium/djvu /tropinone.r To be able to view the DjVu files above, you first need to install LizardTech's DjVu Browser Plug-in v4.1 (http://www.lizardtech.com/download/?x=2 |
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roger2003 (Hive Bee) 09-10-03 12:06 No 458140 |
2-Carbomethoxytropinone to Methyl Ecgonine | |||||||
Reduction of 2-Carbomethoxytropinone to Methyl Ecgonine: Beilstein: H (1909) 22, 196 E I (1919) 22, 547 E II (1929) 22, 151 E III/IV 22, 2098 Other references: Ann. Chem 434, 113 Patent DE408869 J. Am. Chem. Soc. 2356 (1954) J. Org. Chem. 1540 (1959) Berichte 91, 453 Angewandte Chemie 68, 601 roger2003 |
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