N-bromobutanimide → tert-butyl 5-bromo-6-cyclohexyl-4H-thieno[3,2-b]pyrrole-2-carboxylate

Participants

Reaction Conditions

Reaction Steps

A solution (0.2 M) of 6-cyclohexyl-4H-thieno[3,2-b]pyrrole-2-carboxylic acid (prepared as described in example 14, step 8) in THF was treated with tert-butyl N,N′-diisopropylimidocarbamate (2 eq.). The reaction mixture was heated to reflux for 1 h. After cooling down, the mixture was filtered trough a pad of silica gel and washed with AcOEt. Evaporation under reduced pressure of the filtrate gave a residue that was dissolved in DCM. The resulting solution (0.2 M) was cooled at 0° C. and treated with NBS (1 eq.). The reaction mixture was stirred at 0° C. for 1 h, then it was quenched with aqueous Na2S2O3 (saturated solution) and extracted with AcOEt. The combined organic phase was washed with aqueous Na2S2O3 (saturated solution) and brine and dried. Evaporation of the solvent under reduced pressure afforded the title compound (37%) as a solid.

Provenance & Evidence