I got the following exercise question on configurations, which the textbook does not have an explanation that matches this question, so could someone please tell me whether my attempt is correct or not:
A) both the (3R, 4R) and (3S, 4R) products are chiral since for each of them, there are chiral centers and they are not meso (no plane of symmetry observed).
B) since the alkyne anion preferentially attack carbonyl at re face i.e. attack from the bottom viewing from the figure of the question (top view) since the assigned rotation is anticlockwise, I get something like this after attacking (my thinking when drawing this: attack from 'bottom', then rotate the entire molecule such that the carbon linked to the bulky group is on the same plane as the alkyne group): the configuration of this (major product) is S. Moreover, the mixture is optically active since S:R = >50:<50 (not racemic mixture).
May I ask whether this approach is correct or not? And for B), is the reason that re face is attacked preferentially is because of the steric hindrance by CH3, which is out of the plane i.e. on the si face?