Sciencemadness Discussion Board

Diamines alkylation

morsagh - 9-6-2016 at 06:44

What are products of alkylation of some diamine (for example putrescine or cadaverine) with two moles equivalent of ethyl chloride? Does it produce only secondary amines (like 1,6-diethylputrescine) or it goes to tertiary (like 1,1-diethylputrescine) how efective is this for producing secondary compound? What happens if some sterically hindered alkyl halide is used, like terc.-butylchloride? Is the yeld of secondary amine better?

zhiang0113 - 9-6-2016 at 07:26

I think the tertiary amine would be favoured, since the electron-donating effect of the added alkyl group will make the lone pairs on the nitrogen atom more nucleophilic. I suppose bulky substituents would make the amine less nucleophilic though, that should favour the secondary amine more.

Perhaps you could convert it to an amide first (using ethanoyl chloride), then reduce the amide? That would require strong reducing agents like lithium aluminium hydride though.

CuReUS - 9-6-2016 at 07:55

zhiang is right,tertiary amine will be favoured.And bulky substituents favor secondary because they are.......bulky:P

morsagh - 9-6-2016 at 10:35

I can´t find any reference to dialkylation of diamine... So better try aldehyde amine condensation and NaBH4?

clearly_not_atara - 9-6-2016 at 12:02

If you want symmetrical secondary amines, you might be able to do this by alkylating the cyclic aminal formed with benzaldehyde.

CuReUS - 10-6-2016 at 01:30

Quote: Originally posted by morsagh  
I can´t find any reference to dialkylation of diamine...

I found a reference using iodoethane and diaminoethane(similar to your compound) to get the corresponding symmetrical diamine.Sadly,only the pg nos are given(389 and 517,521) not the issue so its very difficult to find.If you are really interested,you could go through each issue till you find it.:(
it is in this journal - http://onlinelibrary.wiley.com/doi/10.1002/ardp.186717901100...
Quote:
So better try aldehyde amine condensation and NaBH4?

instead of NaBH4,you could try hydrogenation
http://pubs.acs.org/doi/abs/10.1021/jo01083a021

Dr.Bob - 10-6-2016 at 04:17

You will most often get a statistical mixture of primary, secondary, tertiary, and sometimes quat. amines. It depends on the amine, the alkylating agent (leaving group and steric bulk), and the conditions. Predicting the exact outcome without some details or previous references is like predicting the outcome of the Superbowl next year. There are many tricks to make specific mono or dialkylations, like using an acetyl group and then reducing that to an ethyl. But all are substrate and alkyl group dependent.