Question

Propose a detailed mechanism for the following transformation. Use curved arrows to show movement of electron pairs and be sure to draw structures of all important reaction intexmediates, State the name of the reaction below. NaOH, EtOH, A OCH3 OCH (11 marks] Draw a reaction energy diagram, and label the product (P), reactant (R), transition states CTS. TS, etc), intermediates (INT1, INT2, etc.) and activation energies (AG', AG , etc.) for a reaction with the following criteria: i. A three-step, endothermic reaction ii. The second-step is the rate determining step iii. The third-step is faster than first-step iv. The first step is endothermic y. The second and third steps are exothermic. [8 marks) 1...6

Answer 1

Answer 1: The name of the reaction is Robinson Annulation named after Robert Robinson. it is used to create cyclic compound by forming C-C bond. Basically it involves Michael addition (1,4-addition) followed by intramolecular aldol condensation to give the final product. As shown in the figure the substrate after formation of enolate ion undergo Michael addition reaction which gives intermediate (I) which tautomerizes to (II). In the presence of base it gives another enolate ion (III) which undergo aldol codensation to give (IV). This is followed by dehydration with removal of water molecule to give the final product.

0CII3NaOH N OCH OCH3 Michael Addition ལོ་ ཡང་ན་ དང་ སྐྱེས་ ལེན་པ་ལ་དབང་བའི་ཚོགས་ OT OCII, EtOH _OCII， EiOII C Intramolecular Aldol Condensation Y OCH -10 Y OCH 0 ) HzCH OH CIl༣ (IV)