[Mpatas]

Synthesis suggestions for different alkyl chains at the para position

[kamiyu]

"pipyridine"

is there any typo??

bipyridine or piperidine

[Mpatas]

Sorry i meant Piperidine

[kamiyu]

For para-sub. alkyl groups, I think this can be easy and straight forward.

First start from 4-bromopyridine and then you lithiate the bromine by n-butyllithium followed by alkyl iodide.

Then you obtain 4-alkylpyridine. You then do hydrogenation of this pyridine (alkyl group not affected) to offer the piperidine

[Mpatas]

Thank you, because i did it starting from deprotonating picoline using LDA. Although, i want also to synthesize  analogues with a secondary alky chain and i was thinking to use 4-ethyl pyridine and do the same. Nevertheless i like your suggestion.

[kamiyu]

1) I do not get the point why you deprotonate picoline....

2) Anyway, for 2^o alkyl chains, doing the electrophile quench may be troublesome, I would suggest you also lithiate the 4-bromopyridine, but add ketone this time. The alcohol formed will be 2^o then reduce this alcohol to alkane.

[Mpatas]

Because i had it in the lab and the protons of the methyl group are acidic enough.My yield was 87 % which is good enough and my product was pure even before column.Anyhow, for the secondary ones, using a ketone is a better choice.

(4-bromopyridine is more expensive)