1,2-Dibromoethane → Ethyl 1-acetylcyclopropane-1-carboxylate

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Reaction Steps

Taking 7-amino-5-azaspiro[2.4]heptane as an example, ethyl acetoacetate is first reacted with 1,2-dibromoethane in the presence of a base to give ethyl 1-acetyl-1-cyclopropanecarboxylate. Then, using bromine, the acetyl group of this compound is brominated to give ethyl 1-bromoacetyl-1-cyclopropanecarboxylate. This bromoacetyl compound is then cyclized with benzylamine to give 5-benzyl-4,7-dioxo-5-azaspiro[2.4]heptane. When this compound is reacted with hydroxylamine hydrochloride, the ketone in the 7-position is converted to an oxime to give 5-benzyl-7-(hydroxyimino)-4-oxo-5-azaspiro[2.4]heptane. This oxime is reduced with lithium aluminum hydride to give a spiro ring-containing aminopyrrolidine compound, viz., 7-amino-5-benzyl-5-azaspiro[2.4]heptane. When the benzyl group of this compound is eliminated by an ordinary procedure, such as catalytic hydrogenolysis, 7-amino-5-azaspiro[2.4]heptane, which is a racemic compound, is obtained. When this cleavage of the benzyl group after the amino group is protected by the reaction of 2-(tert-butoxycarbonylamino)-2-phenylacetonitrile (hereinafter referred to briefly as BOC-ON), 7-tert-butoxycarbonylamino-5-azaspiro[2.4]heptane is obtained.

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