Diastereocontol in Aldol Reactions

Question 1

enolate geometries

Answer 1

E or Z with O having highest priority,
E(O)-enolate only formed when R/X is small
Z(O)-enolate formed when R/X is large

Question 2

enolate TS

Answer 2

cyclic TS

Question 3

chelating aldols

Answer 3

chelating metal enolates react via chair-like TS

Question 4

non-chelating aldols

Answer 4

with very coordinating solvents/non-coordinating metals, open TS with CO dipoles achieving maximum separation, forms syn product regardless of E(O) or Z(O) enolate used