novel route to iso-allylbenzene

stratosphere · Fri Jun 17, 2005 3:53 pm

i found this reaction for creating pheynlcyclopropane from cinnameldhyde using hydrazine hydrate http://www.orgsyn.org/orgsyn/prep.asp?prep=cv5p0929.

this leaves only the problem of cracking the cyclopropane, since petroleum can be cracked using zeolite(alumina and silica) at 540C i would assume that due to ring strain the cyclopropane could be opened under even milder conditions, this being further enhanced by the stability of the benzyl carbocation. in fact the stability of the carbocation is what leads me to believe the primary product would be 1phenyl-1-propene as opposed to 1 pheynl-2-propene.
however i was not able to locate any hard data on thermal ring opening of mono-alkyl/aryl substituted cyclopropanes.

joe_aldehyde · huxleys associate

hey, then you just need real nice equipment and a lot of courage to work with hydrazine...that stuff stinks to high heavens and is a known carcinogen.
i guess you're right about the carbocation,
what you have in the end is not iso-allylbenzene (one carbon atom shorter) but 1-phenylpropene.

stratosphere · Fri Jun 17, 2005 8:05 pm

maybe your right about the name, but what i meant was Ph-CH=CHCH3.

hydrazine hydrate should be better to work with because it can be generated in situo from the fairly safe hydrazine sulphate and a base and should bind to the cin-hyde before it gets a chance to alter your dna.

joe_aldehyde · huxleys associate

didn't think of that, woops. i guess the phenylcyclopropane really doesn't have much choice of what it's gonna do when heated. where did you look for reference of thermal ring opening?

PSY420 · Sun Aug 07, 2005 8:17 am

You should have a look here, they are exactly about the cinnamaldehyde to propenylbenzene rxn :

J.Am.Chem.Soc., 71; 3301 (1949) - H4N2*H2O, NaOH, diethylene glycol
Helv.Chim.Acta, 32; 1817-1832 (1949) - H4N2*H2O, EtOH, NaOEt

--PSY420--