In step (i), dimethylamine (Me2NH) first combines with formaldehyde (CH2O) to form an imine (Me2N=CH2); this ‘Mannich electrophile’ then reacts with 5 in an SEAr reaction. Propose a mechanism for step (i). (5 marks)

I, Me,NH.HCI, CH;0 O C, 3 hours H. HS(CH),NH2, conc. HC OC, 18 hours 5 OH 6 OH NH2