Iron‐Catalyzed Chemoselective Azidation of Benzylic Silyl Ethers

Abstract

Azidation: siloxy groups derived from secondary and tertiary benzyl alcohols can be transformed into azide groups at room temperature using TMSN(3) in the presence of an iron catalyst (TMS=trimethylsilyl). Secondary and tertiary benzylic silyl ethers can be transformed in the presence of primary silyl ethers, and other reactive functional groups, such as alkyl chlorides, α,β-unsaturated esters, and aldehydes, are stable under the reaction conditions.

A Direct Brønsted Acid‐Catalyzed Azidation of Benzhydrols and Carbohydrates

“…Based on the positive results obtained for the benzhydrols, the newly developed methodology was applied to the more challenging carbohydrate substrates. It should be noted that many of the previous methodologies for the preparation of glycosyl azides rely on Mitsunobu‐like conditions with metal azides and hydrazoic acid or by the reaction of unstable glycosyl halides with sodium azide . Remarkably, the conditions used for the benzhydrols led to a 67 % yield with an α/β ratio of 3.3:1 when applied to 2,3,5‐tri‐O‐benzyl‐ β ‐D‐arabinofuranose.…”

“…Due to the explosive nature of sodium azide and hydrazoic acid, investigations into alternative reagents led to methodologies employing azidotrimethylsilane as a commercially available, safe and practical azide source. In these reactions Lewis acid catalysts, such as BF 3 · OEt 2 , NaAuCl 4 , copper triflate, silver triflate, FeCl 3 , MoCl 5 and InBr 3 , were employed to facilitate the substitution by the activation of the hydroxyl group.…”

Gold-Catalyzed Benzylic Azidation of Phthalans and Isochromans and Subsequent FeCl₃-Catalyzed Nucleophilic Substitutions

“…[9][10][11][12][13] We have continuously investigated the iron [14][15][16][17][18][19][20] -or gold [21][22][23] -catalyzed activation at the benzylic position of various skeletons accompanied by the benzylic C-O bond cleavage. During these investigations, the benzylic position of phthalan (1; n=1) as a benzene fused cyclic ether was found to be directly azidated in the presence of a gold catalyst and trimethylsilylazide (TMSN 3 ) without the C-O bond cleavage to give the 1-azido phthalan (2) (Chart 1).…”

Iron‐Catalyzed Arylation of Aromatic Ketones and Aldehydes Mediated by Organosilanes

“…Also recently, iron‐catalyzed reductions of sulfoxides5 to sulfides, as well as chemo‐, regio‐ and stereoselective hydrosilylations of alkenes and alkynes6 have been investigated. Furthermore, deoxygenative transformations of silyl ethers to chlorides7 and azides8 and preparations of ethers through condensation reactions of ketones, aldehydes or alcohols,9 and through reduction of esters10 have been described.…”