I should have read the whole thing first. How about using methyl methacrylate monomer? I have an old chemical experiments book with an experiment in it where they slowly heat the polymer which depolymerizes and the monomer is distilled off. The polymer is also known as acrylic, plexiglass or lucite.
Once you have the phenyl group on the methyl methacrylate, then hydrogenate the double bond on the side chain, make the amide and use the Hoffmann degradation to make amphetamine (if C6H5N2+ was used)
Reduction of cinnamic acid to hydrocinnamic acid: http://www.orgsyn.org/prep.asp?prep=cv1p0311 (http://www.orgsyn.org/prep.asp?prep=cv1p0311)
Note Hofmann degradation of hydrocinnamide here (reference 11): http://www.orgsyn.org/prep.asp?prep=cv3p0720 (http://www.orgsyn.org/prep.asp?prep=cv3p0720)
http://www.geocities.com/dritte123/PSPF.html