Disclosed is a process for the synthesis of lanabecestat ((1r,1&rsquoR,4R)-4-methoxy-5&rsquo&rsquo-methyl-6&rsquo-(5-prop-1-yn-1-ylpyridin-3-yl)-3&rsquoH-dispiro[cyclohexane-1,2&rsquo-indene-1&rsquo,2&rsquo&rsquo-imidazol]-4&rsquo&rsquo-amine), or a pharmaceutically acceptable salt thereof, wherein the process comprises a Suzuki coupling reaction of 5-(prop-1-ynyl)pyridin-3-ylboronic acid with (1r,4r)-6&rsquo-bromo-4-methoxy-5&rsquo&rsquo-methyl-3&rsquoH-dispiro[cyclohexane-1,2&rsquo-indene-1&rsquo,2&rsquo&rsquo-imidazol]-4&rsquo&rsquo-amine, in the presence of a transition metal catalyst such as [1,1&rsquo-bis(diphenylphosphino)ferrocene]palladium(II) chloride or sodium tetrachloropalladate (II), and a base (e.g. potassium carbonate). The process can also be extended to utilise as starting materials compounds including (1r,4r)-6&rsquo-bromo-4-methoxy-5&rsquo&rsquo-methyl-3&rsquoH-dispiro[cyclohexane-1,2&rsquo-indene-1&rsquo,2&rsquo&rsquo-imidazole]-4&rsquo&rsquo(3&rsquo&rsquoH)-thione, (1r,4r)-6&rsquo-bromo-4-methoxyspiro[cyclohexane-1,2&rsquo-inden]-1&rsquo(3&rsquoH)-imine hydrochloride, 2-oxopropanethioamide, N-((1r,4r)-5&rsquo-bromo-4-methoxyspiro[cyclohexane-1,2&rsquo-indene]-3&rsquo(1&rsquoH)-ylidene)-2-methylpropane-2-sulfinamide, (1r,4r)-6&rsquo-bromo-4-methoxyspiro[cyclohexane-1,2&rsquo-inden]-1&rsquo(3&rsquoH)-one, (1r,4r)-6&rsquo-bromo-4-hydroxyspiro[cyclohexane-1,2&rsquo-5 inden]-1&rsquo(3&rsquoH)-one, 6&rsquo-bromospiro[cyclohexane-1,2&rsquo-indene]-1&rsquo,4(3&rsquoH)-dione and 6-bromo-2,3-dihydro-1H-inden-1-one.
