A microwave reaction vial was charged with 4-methoxycyclohex-1-enyl trifluoromethanesulfonate (1069 mg, 4.11 mmol), copper(I) iodide (16.83 mg, 0.09 mmol), tetrakis(triphenylphosphine)palladium(0) (54.6 mg, 0.05 mmol), triethylamine (1432 μl, 10.27 mmol) and dry N,N-dimethylformamide (6849 μl). The reaction was evacuated and purged with nitrogen and a solution of 3,4-bis(benzyloxy)-6-ethynylpyridazine (Intermediate 5; 650 mg, 2.06 mmol) in dry tetrahydrofuran (3 ml) was added before the whole was then stirred in the microwave at 70° C. for 1 hour. Upon cooling, the resulting mixture was partitioned between ethyl acetate and water and the organic extracts were washed with water and brine, dried (MgSO4), filtered and concentrated to afford a brown oil. This was purified by chromatography on silica eluting with 0-75% ethyl acetate in petrol to give 3,4-bis(benzyloxy)-6-[(4-methoxycyclohex-1-en-1-yl)ethynyl]pyridazine (Intermediate 20) as a brown oil (860 mg, 85%).
