alkyl amine adamantane help...

[papa]

does any body know how to alkylate an amino adamantane? that is to prepare adamantane-amine-alkyl??

[Tartaglia]

Are you merely asking how to convert a primary amine into a secondary amine here? Or is there some missing information regarding the adamantyl group?

[hermanntrude]

what is your desired end-product? a secondary amine? a tertiary amine? a quaternary amine? or perhaps even an immine?

[papa]

I would like to make a library if possible. for example: the reaction of 1-amino adamantane with ethyl bromide did go well but when I use isopropyl bromide the yield is very low (I try different methods to make it happen no success yet) any suggestions???

 

though it seems very easy the adamantyl group is very bulky... for example the reaction between alkylamine (such as propylamine) and bromoadamantane is mostly done in a closed chamber at 170-200 oc (pressure tube) and the yield is still low...I would like to make a library if possible. for example: the reaction of 1-amino adamantane with ethyl bromide did go well but when I use isopropyl bromide the yield is very low (I try different methods to make it happen no real success yet) any suggestions???

[Tartaglia]

Even though 1 amino-adamantane is a primary amine the adamantyl group is so bulky it is more likely to act as a base rather than a nucleophile with secondary bromides like 2-bromopropane. You could try better leaving groups like iodide or tosylate triflate, but this may still encourage elimination.

 

Doing the reaction the other way around is fraught with problems. The adamantyl tertiary carbon can not adopt a planar configuration due to ring strain and so this makes Sn1 type mechanism much harder. (Sn2 is out as it can't turn inside out)

[papa]

yes unfortunatly I know all of that, still I think the reaction may be posible in mild conditions through reductive alkylation e.g - adamantane-NH2 + Acetone+ NaBH4 (or any other ketone or aldehyde as well)... what do you think??? no rearengment could never happen in that way, also I can try adamantanone and different amines, though the bulkyness is still a problem...

[Tartaglia]

I think steric hinderance will be a problem with many reactions. I also think the answer is to use a method that utilises more electrophilic reagent to react with the amine and that may be difficult for secondary and tertiary alkyl groups