Synthesis
General procedure for the synthesis of 1,4-dibromoisoquinoline from 1-hydroxyisoquinoline: 2.90 g (19.07 mmol) of 1-hydroxyisoquinoline was mixed with 14.40 g (33.68 mmol) of phosphorus pentabromide and heated to a molten state at 140 °C. The reaction was carried out at a temperature of about 2.5 ° C. The reaction was carried out in the presence of a red liquid. During the reaction, the melt gradually transformed into a red liquid and after about 10 minutes, the reaction mixture solidified and subsequently cooled to room temperature. The solidified reaction mixture was pulverized and slowly poured into ice water. The resulting solid product was collected by filtration and dried in air. 5.50 g of 1,4-dibromoisoquinoline was finally obtained in 96% yield with a melting point of 94-96 °C. The product had an Rf value of 0.66 in a hexane solution of 40% ethyl acetate.
References
[1] Patent: EP1228063, 2009, B1. Location in patent: Page/Page column 32
[2] Patent: WO2007/118602, 2007, A1. Location in patent: Page/Page column 51
[3] Journal of Medicinal Chemistry, 2018, vol. 61, # 17, p. 8029 - 8047
[4] Patent: WO2017/103586, 2017, A1. Location in patent: Page/Page column 38
[5] Patent: US2010/222345, 2010, A1. Location in patent: Page/Page column 97
