2-Bromo-1-benzofuran → 1-(Tert-butoxycarbonylamino)-1-(benzofurylcarbonyl)cyclopropane

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Reaction Steps

Alternatively, the starting bromobenzofuran may be reacted with magnesium metal under standard conditions to prepare the corresponding Grignard reagent, benzofurylmagnesium bromide. This Grignard reagent is then reacted with the Weinreb amide, N-methyl N-methoxy 1-(tert-butoxycarbonylamino)cyclopropane-1-carboxamide, to provide 1-(tert-butoxycarbonylamino)-1-(benzofurylcarbonyl)cyclopropane. This ketone is then reduced under standard conditions, typically with sodium borohydride in methanol or ethanol, to provide 1-(tert-butoxycarbonylamino)-1-(benzofuryl(hydroxymethyl))cyclopropane. This alcohol is then converted to the corresponding acetate and reduced to the corresponding methylene by treatment with samarium iodide as previously described. The resulting 1-(tert-butoxycarbon-yl)-1-(benzofurylmethyl)cyclopropane is treated with acid under standard conditions to provide the compounds of the present invention. If necessary or desired, the Weinreb amide may be reduced by reaction with lithium aluminum hydride to provide the corresponding aldehyde essentially as described by Fehrentz and Castro (Synthesis, 676 (1983)). This aldehyde is then reacted with the Grignard reagent previously described to prepare 1-(tert-butoxycarbonylamino)-1-(benzofuryl(hydroxymethyl))cyclopropane, which is then subjected to the reaction conditions previously described to prepare the compounds of the present invention. The requisite Weinreb amide, N-methyl N-methoxy 1-(tert-butoxycarbonylamino)cyclopropane-1-carboxamide, may be prepared from the commercially available 1-amino-1-carboxycyclopropane by standard methods well known in the art.

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