[science123]

For both the rxns the electron withdrawing group is facing down. Is that the only product that will form or would we get the ketone group facing up (on wedge) also ?

Also in the second rxn, can we have methyl group facing down and ketone up as a second product? Would that violate the endo rule ?

I understand endo rule for bicyclic compounds but for some reason I am not sure if it also applies to other six membered rings as well.

[sjb]

In both these cases, without any chiral influence, the products you propose ("ketone group facing up" with or without extra methyl) are the same as the products you have drawn, due to the symmetry of the diene.

[science123]

In both these cases, without any chiral influence, the products you propose ("ketone group facing up" with or without extra methyl) are the same as the products you have drawn, due to the symmetry of the diene.

What would be a good example where endo product (monocyclic) is the only product formed using an acyclic dienophile?

[orgopete]

I don't know that you will find people wanting to describe the principle as the endo rule without an endo product, but the principle still holds none the less. If you react cis-1,3-pentadiene with maleic anhydride, you should get the cis,cis-adduct. The trans would give the cis,trans-product. These will not be the "only" product, but the major products.

It failed to show the questioned stereochemistry in the posted examples as the double bond does not have cis-trans isomers with regard to the dienophile stereochemistry in the product.