Dibutyl squarate → 1-Butoxy-2-(3-bromopropylamino)-1-cyclobutene-3,4-dione

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Reaction Steps

The solution of bromopropylamine base, cooled to 0° C., was slowly added dropwise with vigorous stirring and cooling to maintain the temperature below to the methanolic solution of Step A containing 1,2-dibutoxy-1-cyclobutene-3,4-dione. The mixture was stirred at 20° C. for 2 hours, polish filtered through diatomaceous earth, washed with methanol (2×0.25L) and the filtrate was added over a period of 1 hour with vigorous stirring to water (31.1L). The mixture was stirred at 0° C. for 2 hours. The solid was collected by filtration, washed with water (3×2L) and dried to vacuo at 50° C. to give 2137 g (84% yield) of the title compound as an off-white solid; m.p.=69° C.

Provenance & Evidence