B(C6F5)3‐Catalyzed Chemoselective Defunctionalization of Ether‐Containing Primary Alkyl Tosylates with Hydrosilanes

• Published in: Angewandte Chemie International Edition Vol. 56; no. 12; pp. 3389 - 3391
• Main Authors: Chatterjee, Indranil, Porwal, Digvijay, Oestreich, Martin
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 13.03.2017
• Edition: International ed. in English
• Subjects: alcohols; boron; deoxygenation; Ethers; reduction; silanes; deoxygenation; silanes; alcohols; reduction; boron
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201611813

Catalytic C(sp3)−O bond cleavage promoted by B(C6F5)3 /Et3SiH proceeds preferentially with primary tosylates in the presence of primary and secondary silyl ethers and aryl ethers. This reactivity difference enables the chemoselective defunctionalization of several 1,n‐diols, and the efficiency of the new procedure is highlighted by the selective deoxygenation of the hydroxymethyl group of an orthogonally protected carbohydrate. Tosylates with an adjacent phenyl group are cleaved with anchimeric assistance. The weakest link: Hydrosilanes activated by B(C6F5)3 are known to cleave ethers as well as silyl ethers. However, more reactive tosylates are cleaved prior to those ethers, which allows for the chemoselective deoxygenation of diols and polyols. Other functional groups such as carboxyl groups are also tolerated. Defunctionalization of phenethyl tosylate motifs proceeds with anchimeric assistance (rearrangement).