[Acadasol]

I have tried to reduce a cyclic amide (Lactame) with LiAlH4 and at all the time, I have repeatedly gotten yield of 58%. Does anyone have an idea as to why the reduction doesn't got to completion with LiAlH4? Thanks!

[Syrnyk]

Since LiAlH4 is a reducing agent for amides, it should successfully reduce your Lactam group in theory. Given your 58% yield, it sounds to me like some type of reaction occurred, but side reactions also occurred. Perhaps a procedural step was the issue, as you did not clarify the process that you used to perform your reduction. For instance, did you correctly perform an acid work up with your solution, presumably dissolved in diethyl ether?

[discodermolide]

Your product will be an amino alcohol. This may well react with LiAlH₄ and reduce it's reducing ability. Much like treating LiAlH₄ with tert-butanol to modify its reactivity.
Try the reaction at reflux.
Try adding more LiAlH₄.
Try a different reducing agent.

[Acadasol]

Since LiAlH4 is a reducing agent for amides, it should successfully reduce your Lactam group in theory. Given your 58% yield, it sounds to me like some type of reaction occurred, but side reactions also occurred. Perhaps a procedural step was the issue, as you did not clarify the process that you used to perform your reduction. For instance, did you correctly perform an acid work up with your solution, presumably dissolved in diethyl ether?

In the reference paper, confidentially, the yield was also 58%. So, I was thinking perhaps LiAlH4 couldn't reduce all of the starting material. I worked the reaction up by gradually dropping crystals of NaSO4 into the reaction mixture to evolve hydrogen gas. And the organic layer was separated with diethyl ether. My product is a cyclic amine. Is it possible that some of the spots that I get reduce the reducing ability of LiAlH4

[orgopete]

In my opinion, the mechanism suggests a difficulty in this reaction. The problem as I see it is that it is difficult to eliminate the oxygen. It must come out as an aluminum oxide. As I recall, typically procedures use an incremental addition of LAH and the yields are never as high as ketone or ester reductions.

[kriggy]

I tried to reduce macrocyclic amide to amine by LiAlH₄ and it didnt work at all. After literature search, I found out that others had same problem reducing very similar compound using LiAlH₄, BH₃ etc.. about 5 reducing agent tried and none of those worked.

[Acadasol]

Your product will be an amino alcohol. This may well react with LiAlH₄ and reduce it's reducing ability. Much like treating LiAlH₄ with tert-butanol to modify its reactivity.
Try the reaction at reflux.
Try adding more LiAlH₄.
Try a different reducing agent.

My product is actually an amine. The CO was reduced to CHI with 2 equivalent LiAlH4

[kriggy]

CHI? you mean CH₂?

It doesnt mean anything, some aminoalcohol still can be formed and reduce the reactivity of LAH. DO you know what are the other products (the rest 40%)?

[Acadasol]

CHI? you mean CH₂?

It doesnt mean anything, some aminoalcohol still can be formed and reduce the reactivity of LAH. DO you know what are the other products (the rest 40%)?

Yes, I meant methylene. That was a typo. Meanwhile, I didn't collect the other product. But, there were other spots.

[discodermolide]

With 40% of other products it would be worth isolating them and finding out what they are. It may help you understand what is going on in this reaction.

[phth]

try using a lewis acid and a cryptand.

[k1mng]

Hey Acadasol, sorry to hear about your unsatisfactory yields... even the most reliable reactions can sometimes give us crappy results... For context can you perhaps show us what you're trying to reduce so that the issue can be troubleshooted and solutions given from an informed perspective?