was wondering if someone could help me write a mechanism for the synthesis of methyl E-4-methoxycinnamate from p-anisaldehyde. and suggest a reason why the cyclic intermediate might have two important groups in a trans relationship that could favor the E-alkene.

Answer 1

Have you tried to draw a mechanism on one of these help boards. Tough to do. Actually, almost impossible to do.

Answer 2

How are you making it?

MeOAr-CHO + wittig -> MeOAr-CH=CHCOOMe

or a Wadsworth Emmons?

Answer 3

If it is a Wittig you should get the Z product unless it is the Schlosser Modification which gives the E product.

There is a good description of the Wittig mechanism on the Wikipedia page

http://en.wikipedia.org/wiki/Wittig_reaction

Which shows the cyclic transition state.