[lithiumuranium]

Can H₂, Pd (high pressure) be used to reduce a non-aryl ketone to an alkane, when other groups are too sensitive to use clemmensen or wolff-kishner reduction?

[discodermolide]

Can H₂, Pd (high pressure) be used to reduce a non-aryl ketone to an alkane, when other groups are too sensitive to use clemmensen or wolff-kishner reduction?

I found this reference:
Poly(ethylene glycol) (PEG) (400) has been found to be a superior solvent over ionic liquids by severalfold in promoting the hydrogenation of various functional groups using Adams' catalyst. Both the catalyst and PEG were recycled efficiently over 10 runs without loss of activity, and without substrate cross contamination.
S. Chandrasekhar, S. Y. Prakash, C. L. Rao, J. Org. Chem., 2006, 71, 2196-2199.

on this page: http://www.organic-chemistry.org/synthesis/C1H/reductionsalkenes.shtm
the 10th reference down the page.

[Dan]

What about Mozingo reduction?

[orgopete]

What about Mozingo reduction?

I agree.

[lithiumuranium]

This is where I got the question from http://www.icho2012.org/44th_International_Chemistry_Olympiad_Preparatory_Problems.pdf (page 45).

In the reaction from [F] to [G], it is apparent that the ketone gets reduced to a methylene group if you look at the product that comes after . However, I thought that H₂, Pd reduced ketones to alcohols only. So I didn't understand why they used catalytic hydrogenation (does it also work in this case?) when this is a clemmensen reduction.

this is my solution: http://postimage.org/image/d112bxme9/168e3932/

[Dan]

This is where I got the question from http://www.icho2012.org/44th_International_Chemistry_Olympiad_Preparatory_Problems.pdf (page 45).

Haha, there's ~4 months of my PhD on p46/47!

Back to topic: I think what we are seeing here is reduction of the ketone to an benzylic alcohol. Generally the RCH₂-OH is not cleaved by H₂, Pd - but if R is an aromatic group then it is cleaved (hydrogenolysis). Benzyl (CH₂Ph) ethers are commonly used as alcohol protecting groups because they are easily cleaved this way.

Protecting group cheimistry:

PhCH₂-OR + H₂ (Pd cat.) PhCH₃ + HOR

This example:

ArC=O(R) + H₂ (Pd cat.) ArC-OH(H)(R)
ArC-OH(H)(R) + H₂ (Pd cat.) ArCH₂R + H₂O