To a 1M solution of ethylmagnesium bromide in THF (1.3 mL, 1.3 mmol) under a nitrogen atmosphere, was added dropwise cyclopropylethyne (70% in toluene, 0.154 mL, 1.3 mmol). The reaction mixture was heated at 50° C. for 15 mins then allowed to cool down to RT. A solution of 2-azido-8-bromo-4,5-dihydro-6-oxa-3-thia-1-aza-benzo[e]azulene (425 mg, 1.3 mmol) in THF (1.5 mL) was then added dropwise. The reaction mixture was stirred at RT for 2 h, quenched with aqueous saturated ammonium chloride and diluted with ethyl acetate. The organic layer was washed with brine, dried (Na2SO4) and concentrated in vacuo. The resultant residue was triturated with 20% ethyl acetate/cyclohexane and filtered to afford the title compound as a pale yellow solid (373 mg, 64%). LCMS 110142391 (Method B): RT=4.40 min, [M+H]+=390. 1H NMR (DMSO-d6): 8.20 (1 H, d, J=8.6 Hz), 7.71 (1 H, d, J=0.7 Hz), 7.36 (1 H, dd, J=8.6, 2.1 Hz), 7.30 (1 H, d, J=2.1 Hz), 4.40 (2 H, t, J=5.0 Hz), 3.41 (2 H, t, J=5.0 Hz), 2.70-2.63 (1 H, m), 1.21-1.15 (2 H, m), 0.91-0.86 (2 H, m).
