2-tert-Butyl-1,3-diisopropylisourea → tert-butyl 6-cyclohexyl-4H-thieno[3,2-b]pyrrole-2-carboxylate

Participants

Reaction Steps

A suspension of 6-cyclohexyl-4H-thieno[3,2-b]pyrrole-2-carboxylic acid (1 eq., prepared as described in WO2005/023819) in dry CH2Cl2 (0.19 M) was treated with tert-butyl N,N′-diisopropylimidocarbamate (2 eq.). The resulting clear solution was heated to reflux for 20 h. Addition of a further equivalent of isourea was required after 16 h to drive the reaction to complete conversion. After cooling down the solvent was evaporated in vacuo giving a residue that was purified by flash chromatography (PE:EtOAc, 10:1) affording the title compound (57%). 1H-NMR (400 MHz, DMSO-d6, 300 K, δ) 11.12 (bs, 1H), 7.55 (s, 1H), 7.08 (s, 1H), 2.60-2.50 (m, 1H), 1.99-1.67 (m, 5H), 1.51 (s, 9H), 1.45-1.19 (m, 5H). MS (ES+) m/z: 306 [M+H]+.

Provenance & Evidence