Synthetic route to hydroxychloroquine
This took a bit of thinking about but here is a viable route from commercially available bulk materials. 

Start with nitroethane, deprotonate ($\ce{t-BuOK}$ in THF would be my choice, but $\ce{NaOEt/EtOH}$ should do it) and react with the commercially available dioxane protected 3-bromopropanal. Reduce the nitro group - alkyl nitro groups are tricky to reduce, I've found Hg/Al amalgam to be pretty good but others may have different conditions. There's a recent review of reductions$\ce{^{[1]}}$. The product of this will do the SNAr with 4,7-dichloroquinoline, I would try $\ce{K2CO3/MeCN}$ for this, but here are plenty of other possible conditions. This is  a good point to purify, then reveal the masked aldehyde by acid hydrolysis and do a reductive amination with the commercially available N-Ethylethanolamine to give the desired product.



Reference


Manuel Orlandi, Davide Brenna, Reentje Harms, Sonja Jost, and Maurizio Benaglia, Organic Process Research &amp; Development 2018 22 (4), 430-445
DOI: 10.1021/acs.oprd.6b00205