The Vespiary

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?

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+MeOLi) = >1000.

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 ? ;)

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?

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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) (https://www.thevespiary.org/rhodium/Rhodium/djvu/tropinone.reduction-2.djvu)

(https://www.thevespiary.org/rhodium/Rhodium/djvu/tropinone.reduction-2.djvu)

Stereochemistry of the Reduction of Tropinone
A. H. Beckett et. al.

Tetrahedron, Vol. 6, pp. 319-330 (1959) (https://www.thevespiary.org/rhodium/Rhodium/djvu/tropinone.reduction-1.djvu)

(https://www.thevespiary.org/rhodium/Rhodium/djvu/tropinone.reduction-1.djvu)

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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 (http://l2.espacenet.com/dips/viewer?PN=DE408869&CY=gb&LG=en&DB=EPD)

J. Am. Chem. Soc. 2356 (1954)
J. Org. Chem. 1540 (1959)
Berichte 91, 453
Angewandte Chemie 68, 601