Abstract1H and 13C Nuclear magnetic resonance spectra of brominated dihydrothebainones, needed for the closure of the oxygen bridge of morphinans to form morphine derivatives, were studied. Bromination of (‐)‐dihydrothebainone (1) yielded successively 1‐bromo‐, 1,7α‐dibromo‐, and 1,5β,7α‐tribromo‐dihydrothebainone (2,3,4). 1‐Bromo‐O4‐methyldihydrothebainone (12) gave, after bromination, a stable crystalline l,5β,7α‐tribromo derivative (15). A 5β,7α‐dibromo derivative (9) was formed also starting with l‐methyldihydrothebainone (7).Closure of the oxygen bridge in 1,5β,7α‐tribromodihydrothebainone (4) in boiling ethanol, yields an equilibrium mixture of 1,7β‐ and 1,7β‐dibromodihydrothebainone (5:6, ∼ 35 : 65). 5β,7α‐Dibromo‐l‐methyldihydrothebainone (9) gave the same result.13C NMR spectra of the model compounds cyclohexanone, 2‐bromo‐, 2,2‐dibromo‐, cis‐ and trans‐2,6‐dibromo‐cyclohexanone were studied.