Of course, cinnamyl alcohol is notable for little else but being even more useless than cinnamaldehyde... some people never learn.

Actually, palladium acetate will "walk" double bonds across a molecule via a sequence of additions and eliminations - allylic alcohols yield enols, which tautomerize to aldehydes or ketones - with cinnamyl alcohol, 3-phenylpropanal is produced. This can almost certainly be rearranged to P2P using cold H2SO4. PhCH2CHOHCHO --> PhCHOHCOCH3 (L-PAC) has been done.

Li/NH3 will reduce cinnamyl alcohol to propenylbenzene. It appears likely to Assyl that HI would effect a similar reduction.

Might as well blow the lid on a few old ideas Assyl has kicked around...

Cyanide adds via 1,4 conjugate addition to enones in ethanol. For those familiar with organic chemistry, where this is headed should be obvious. PhCH(CN)CH2CHO would be the product - again, rearrange with cold H2SO4 to PhCH(CN)COCH3, and then reflux in aqueous H2SO4 to hydrolyze the CN to COOH and decarboxylate (beta keto decarboxylation proceeds quickly and easily).

Polverone and madscientist on Sciencemadness.org outlined a procedure for making cyanide cheaply and easily in large quantities - sodium cyanate is produced from a sodium base (hydroxide, carbonate, or bicarbonate) and urea, and then reduced with charcoal to cyanide over a charcoal fire fanned with a hairdryer to white heat.

It should be possible to reduce cinnamaldehyde directly to 3-phenylpropanal using sodium dithionite, so long as it is not done at reflux. At higher temperatures, the carbonyl tends to be reduced to an alcohol. Dithionite is selective for the double bond in enones.

Zn in AcOH will reduce enones to ketones as well as Li/NH3. The latter is generally the preferred procedure in a synthetic laboratory due in part to it producing an enolate, allowing some slick one pot chemistry to be done.

It may be possible to effect hydrocarboxylation of cinnamaldehyde using oxalic acid (CO source) and sulfuric acid, followed by rearrangement and decarboxylation to yield P2P (Koch-Haaf hydrocarboxylation). [Haaf, W. Chem. Ber. 1966, 99, 1149; Christol, H.; Solladie, G. Bull. Soc. Chim. Fr. 1966, 1307]

As shown by CycloKnight on Sciencemadness.org, cinnamaldehyde is easily converted to benzaldehyde - and acetylides are good nucleophiles, adding easily to aldehydes. Acid-catalyzed hydration of such an adduct should yield L-PAC. Calcium carbide is trivial to source (carbide being the traditional name for dibasic acetylide).

or just cassia oil and 3 moles of koh soln. and a cannizarro rxn to get both products.
cassia oil is dirt cheap at the organic hippie stores.
cinnamic acid is easy to separate out.
of course cassia oil is mostly cinnamaldehyde