Hydrogen Bromide → N-(3,4,4-trifluoro 3-butenyl)phthalimide

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Reaction Steps

The compounds of the formula above wherein X, Y, and Z are F and Q is a --CH2N-- derivative are generally prepared by first obtaining the desired trifluoroalkenylamine, which when n equals 1 is 3,4,4-trifluoro-3-butene-1-amine. One method of preparing this compound is disclosed in Example 6 of U.S. Pat. No. 4,952,580, the full text of which is incorporated herein by reference. The present invention provides an improved and novel method of making this compound. Surprisingly, 4-bromo-1,1,2-trifluoro-1-butene, which is commercially available, may be directly converted by first reacting it with a tosylate salt, for example, silver tosylate, a mesylate salt, or other sulfonic acid leaving group. The resulting intermediate, for example, 3,4,4-trifluoro-3-butene-1-tosylate or 3,4,4-trifluoro-3-butene-1-mesylate, is a novel compound. This step is followed by conversion to the phthalimide derivative using a phthalimide salt, such as potassium. Advantageously, this may be accomplished without first isolating the tosylate or mesylate intermediate. The phthalimide is then converted to the desired amine by reaction with hydrazine. This novel process for preparing 3,4,4-trifluoro-3-butene-1-amine has the advantage of having an improved yield compared to the prior reported synthesis method, which is at least partially attributable to avoiding the elimination of hydrogen bromide during the conversion of the bromo compound. N-(3,4,4-trifluoro-3-butenyl)phthalimide is thus produced in greater than 80 percent yield and converted to the desired amine in greater than 85 percent yield. Also, advantageously, when silver tosylate is the reactant chosen to provide the leaving group, the silver ions may be recovered and silver tosylate regenerated.

Provenance & Evidence