I'm attempting to reduce a aliphatic nitrile to an aldehyde, but not reduce a nearby ester. I've found the Stephens Reduction (though there is little recent literature) and other Pd/C methods with formate or hypophosphite, can anyone suggest a good publication with this type of selective reduction? Thanks a lot!
Murphy,
Please, you may find the answer to your question in
---Boyer, Francois-Didier et al,Tetrahedron Letters, (2002) 43(46), 8277-8279
---Boyer, Francois-Didier et al, European Journal of Organic Chemistry, (7), 1184-1190; 2003
---Maeda, Hiroshi and Itaya, Nobushige, Jpn. Kokai Tokkyo Koho, 2002047263, 12 Feb 2002
Good luck
I would recommend against using DIBAL, the inherent reactivity of esters is greater than that of nitriles; so unless there is a large steric difference you will not get your desired product.
You need a reductive method that gives a relatively stable imine intermediate, the Stephens reduction is quite harsh (anhydrous HCl and SnCl2) so there will not be many references. You could also try using a less powerful hydridic reductant which is a good lewis acid, such as AlH3 or a hindered borane derivative (catecol borane, 9-BBN, BCy2H etc.) although over reduction to the amine may be an issue and it may take a bit of heat.
Try Raney-Ni and refluxing formic acid. The iminium formate salt should be fairly stable and will give the aldehyde on aqueous work up.
http://reference.sabinet.co.za/webx/access/electronic_journals/chem/chem_v61_a27.pdf here is a recent review for the transfer hydrogenation of nitriles with Raney-Ni
Please find some more conditions in addition to above links.Which might be use ful
1) * Formation of N-alkylnitrilium ions and their reduction to N-alkylaldimines by organosilicon hydrides. (JOC, 46, 602 ( 1981).*
2) Organic Syntheses, Coll. Vol. 6, p.631 (1988)
2) Triethylammonium hypophosphite Hydrate/ Ra Ni
3) Formic acid / Ra Ni
* Author claims selective reduction of nitriles in polyfunctional substrates.
Thank you Eric and Kachapur, RaNi with HNEt3 hypophosphite looks like the ticket.
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