[S:1]1[C:5]([CH2:6][C:7]#[N:8])=[CH:4][C:3]2[CH:9]=[CH:10][CH:11]=[CH:12][C:2]1=2.Br[CH2:14][CH2:15][CH2:16]Br.[OH-].[K+].Cl>CCOCC.CS(C)=O>[S:1]1[C:5]([C:6]2([C:7]#[N:8])[CH2:16][CH2:15][CH2:14]2)=[CH:4][C:3]2[CH:9]=[CH:10][CH:11]=[CH:12][C:2]1=2
A solution of benzo[b]thiophen-2-acetonitrile (8.05 g) and 1,3-dibromopropane (5.2 ml) in ether (50 ml) was added dropwise under nitrogen over 1 hour to a stirred, ice-cold suspension of finely-powdered potassium hydroxide (13.53 g) in dimethyl sulphoxide (100 ml). When the addition was complete, the mixture was stirred at ambient temperature for 4 hours, then it was added to ice-cold water (200 ml). The resulting mixture was acidified to pH4 by the addition of concentrated hydrochloric acid, then the product was extracted into ether (3×200 ml). The combined extracts were washed with water (500 ml), dried (MgSO4), and the solvent was removed in vacuo to give 1-(benzo[b]thiophen-2-yl)cyclobutanecarbonitrile as a red oil (8.16 g) which was used without purification.
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