Question

How to convert the compounds into wedge dash projection please? For example in question 1, how do we know that both methyl group and CN group is going into the plane whereas both the H groups are coming out of the plane?

Predict stercochemistry me if no its connected to need to show Eg H NO2

Answer 1

This is an example of Diel's alder reaction in which major product formed is the one which follows 'endo' approach also called a endo rule

according to this rule the electron withdrawing group in the dienophile (alkene) should be pointing towards (i.e endo means toward inner side) of the developing pi bond

so in the first case the CN group should be pointing down toward inner side and the corresponding Me on the diene should be on the same side as well for proper overalp hence relative stereochemistry of both the group is on the dash. This is sometimes refer to as cis principle meaning both the group on the diene and dienophile must end up cis in the final product

In the last two eample you have to draw CHO group and NO2 group respectively in the dash so as to follow endo rule

D NO2 NO2 CHO "сно