Ring Opening of Aziridines by Pendant Silanols Allows for Stereospecific Preparations of 1′-Amino-tetrahydrofurans

We have developed a highly stereospecific cyclizationof aziridinesilanols into 1 '-amino-tetrahydrofurans. Our protocol of stirringa substrate with 10 mol % Sc (OTf)(3) and 1 equivalent ofNaHCO(3) in CH2Cl2 is mild and compatiblewith a range of activating aziridine N-substituents(including tosylates, mesylates, and carbamates) and functional groupson the alkyl chains (including substituted aryl rings, alkyl bromides,and alkyl ethers). In all cases examined, trans di-substitutedaziridine silanols give products with an erythro configuration;conversely, cis di-substituted aziridine silanolsgive products with a threo configuration. While literaturesyntheses of 1 '-amino-tetrahydrofurans exist, only one example,contemporaneous with our work, uses a similar cyclization for theirconstruction. Control experiments demonstrate that, for this transformation,the silanol is not particularly privileged, and a variety of protectinggroups on the alcohol (including other silicon protecting groups,benzyl ethers, and MOM ethers) are compatible with product formation.