What a simple but excellent design idea. It will increase serotonin release/serotonin reuptake more than plain methylphenidate. I think the reason it's only just surfaced is that ritalinic acid used to be available commercially VERY cheaply so ethylphenidate & isopropylphenidate would be the next obvious steps (just dehydrate with a different alcohol).. I am going to guess that it's very much like methadrone/pyrophenidone_.
Now, this is also important because it begs the question 'will other ring substitutions give Ritalin derivatives 5HT2a affinity?' because if so, Sasha's Pihkal & Tihkal might need a third volume - Pheikal (Phenyl piperidine ester IHKAL DMBPMM (2-(2,5-dimethoxy-4-bromobenzyl)-6-(2-methoxyphenyl)piperidine) suggests that it is so.
I've tried p-Me Aminorex and that is a serotonin releaser/serotonin reuptake inhibitor BUT it will not fit into the 5HTaa receptor. Believe me, we tried.
Interestingly ethylphenidate is quite a bit more serotonergic than 4-methyl-methylphenidate:
I don't think any of the aryl substituted MPH analogs have significant SERT affinity (at least relative to their DA/NE affinity). Unless you consider naphthalene an aryl substitution (the naphthalene methylphenidate analog supposedly quite active at the SERT . But not so sure a napthalene could be considered an aryl substitution, i suppose technically it is (i'm not much of a chemist).