Question

QUESTION 11 Listed below are four reaction schemes (Scheme A-D), as well as a synthetic target. Select which scheme will give the desired product with the greatest selectivity, and briefly describe why (both need to be included for full credit): Scheme A Me LDA -78 °C Ph Н. -78 °C to 25 °C 25 °C Scheme B Fo Me LDA 25 °C Ph H 25 °C to -78 °C -78 °C Scheme C

Answer 1

Answer The tonget molecule is ال) 0 11 Me ph Oli () Me مان Ia • Me Ph Phi 111 Me РИ So we know & me Me LDA Me CH A is kinetic enclate as double bond is less substituted 6 is thermodynamic enolate as double bond is more substituted . here kinetic enolate is ro required get the tanget molecub. both kinetic and their mody manic In presence sence of LDA ena late can from

get to kivelic enolate , low tempareture is required as low tempareture Javours kinélix product. So we have to carry out the synthesis at low tempareture here only schene-c is totally following low temperature il -78°c. So this is the right choise. If giving room tempareture at any step, thermodynamic enolate will farm that can not be com wanted to the desired product. we are LDA -78% hit 000 Me Me -78€ Phytt so .78°C olu Me Ph. so scheme -c will give desired foroduct with greatest slotecteritz