will KMnO4 oxidise an allybenzene to its benzaldehyde, or does the allybenzene need to be isomerized  to a propenylbenzene first? Any thoughts on how to reduce solvent volume on this rxn would be also be appreciated.

thanks as always

Sure it will, but it will happen at the wrong position. Every synthesis I've seen wants to make a 1,2-glycol or epoxide or acetyl/formyl glycol, not the 2,3-glycol etc. (I would expect a 2,3-glycol to rearrange to the terminal ketone (ie aldehyde) but maybe you'd get a 2-propanone? more input needed on that topic...) Without access to good analytical equipment, I think I'd choose to isomerize to be safe.

Reducing solvent volume should be easy, accomplished by slowly dripping a more concentrated solution of KMnO4 onto the solution. More experimental details are needed on that area, I haven't seen anyone attempt it yet.

Why would you want a benzaldehyde instead of a ketone? Trying to explore a  new PEA.
VL_

Trying to explore a new PEA. or the hypothetical viability of one.

chromic - yah, its just such a lousy yeilding rxn, that it seems more attractive if it could be done with a raw material. Adding two steps adds 40% to overall process.