[physstudent1]

This is the reaction I thought that it would form a cyclohexane with CH3 and H3C=O groups on neighboring carbons trans with a double bond on the opposite side of the ring.  This isn't the answer though, I may be having some confusion about if it should be endo or exo product although I have tried them both in trans with wedges and dashes and both are wrong I'm not really sure can someone help.

[macman104]

Can you show the product you are drawing?

[physstudent1]

[physstudent1]

anyone know why this is wrong?

[noodlesoup]

if i m not wrong, it should be exo. i think you draw the subtituents as endo only when your diene is the ring, but in this case, it is not, so it should be exo. from your product picture, it looks reasonable to me. it is trans, so the methyl group you would use dash line and the the remaining substistuent you would use a solid or wedge line to show the trans relationship.

[nj_bartel]

I think you should be forming the endo product.  The transition state with the electron withdrawing substituent (assuming it has sp/sp² hybridized components underneath the diene is most stable because of p orbital overlap.

[physstudent1]

but im getting it wrong

[kiwi]

I think you should be forming the endo product.  The transition state with the electron withdrawing substituent (assuming it has sp/sp² hybridized components underneath the diene is most stable because of p orbital overlap.

seconded. from my back-of-an-envelope sketch i get the enantiomer of the product you have drawn, although obviously there will be only diastereoselectivity so your enantiomer should work too.

[physstudent1]

I tried inputting the enatiomer after my first attempt was wrong..(just on a guess) but I still got it wrong

[physstudent1]

UGH, looks like I was getting it right all along but I had the H's on the diagram which were supposed to be implied ...sigh anyway, I know endo is usually favored but how do I know which subsituent on the dienophile will be the endo ones is it always the ones on the left?  How do I know which are the exo and if endo is usually favored when will it be exo addition? Also does this only really matter if I'm adding it to a cyclic diene?

[kiwi]

UGH, looks like I was getting it right all along but I had the H's on the diagram which were supposed to be implied ...sigh anyway, I know endo is usually favored but how do I know which subsituent on the dienophile will be the endo ones is it always the ones on the left?  How do I know which are the exo and if endo is usually favored when will it be exo addition? Also does this only really matter if I'm adding it to a cyclic diene?

if you think about the transition state its relatively easy. it helps to have a set of molecular models to get it straight in your head. your dienophile is normally going to be an electron-deficient alkene, with an ester/ketone/aldehyde group on one end. The pi-system of this electron withdrawing group interacts with the diene, such that the favoured transition state has the electron withdrawing group directly under/over the diene. so if you can sketch that on a piece of paper (or build it in models) then its quite clear what the dominant products will be.