Q4(a). Enamine bromination with ring contraction; Dakin reaction
Suggest a mechanism for the following reactions:
(i) [structure] → (Br₂, NaOH) [structure]
(ii) [structure] → (H₂O₂, NaOH) [structure]
Answer in brief
(i) Bromination, hydroxide addition, aziridinium formation and ring opening give 1,7,7-trimethyl-1-azaspiro[4.5]decan-6-one . (ii) The Dakin reaction (HOO⁻ addition, aryl migration, formate hydrolysis) gives 2-chlorohydroquinone .
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Coversintramolecular displacementiminium ionhemiaminalneighbouring-group participationaziridinium ion
All parts of Question 4
- 4(a) Enamine bromination with ring contraction; Dakin reaction10 marks
- 4(b) Claisen ester condensation: why R₂CHCO₂Et fails10 marks
- 4(c) Fischer indole synthesis: 2-phenylindole10 marks
- 4(d) Stabilised and unstabilised ylids; E/Z selectivity in the Wittig reaction10 marks