N-Bromosuccinimide (NBS) — Selective and effective catalyst for trimethylsilylation of alcohols and phenols using hexamethyldisilazane and their regeneration under mild and neutral reaction conditions

Abstract

Structurally diverse alcohols and phenols were trimethylsilylated in a clean and efficient reaction with hexamethyldisilazane (HMDS) based on the use of a catalytic amount of N-bromosuccinimide under both dichloromethane and solvent-free conditions at room temperature. Deprotection of trimethylsilyl ethers was also be achieved efficiently in the presence of a catalytic amount of NBS in methanol at ambient temperature.Key words: N-bromosuccinimide, solvent-free, alcohols, phenols, hexamethyldisilazane, trimethylsilyl ether, catalyst, detrimethylsilylation.

Trimethylsilylation of Hydroxyl Group with 1,1,1,3,3,3‐Hexamethyldisilazane (HMDS) Catalyzed by Tribromomelamine (TBM)

“…A reaonable mechanism of this reaction is shown in Scheme III based on reported pathway in literatures, 14,16,42 our observations, and the obtained results. Tribromomelamine acts as a source of Br + , which polarizes the Si-N bond in HMDS to produce active silylating agent.…”

N‐Bromosuccinimide Catalyzed One‐pot and Rapid Synthesis of Acetamidobenzyl Naphthols under Mild and Solvent‐free Conditions

“…The actual role of NBS is not clear. However on the basis of previously reported mechanism for applying NBS to organic transformations 26 and our observation in the course of reaction, one explanation for this process is that the NBS releases Br ＋ in-situ, 27 which can act as an electrophilic species and in-situ ortho-quinone methide as a reactive intermediate was a Yields refer to the pure isolated products. All known products have been reported before in the literature and were characterized by comparison of IR and NMR spectra with the authentic samples.…”

Boric acid as cost-effective and recyclable catalyst for trimethylsilyl protection and deprotection of alcohols and phenols

“…We were then interested in whether the same catalyst could be employed for trimethysilylation of phenolic compounds. Under the same conditions as above, most of the tested phenols (Table 3, entries [16][17][18] were smoothly converted into the corresponding tms ethers in good yields. No elimination and rearrangement by-products were observed at all.…”

“…Although several methods have been reported for the deprotection of trimethylsilyl ethers, [14][15][16][17] to the best of our knowledge there are only two reports for both protection and deprotection of alcohols and phenols as trimethylsilyl (tms) ethers in the presence of catalyst. [18][19] Therefore, there is still a demand to develop environmentally acceptable protocols for the trimethylsilylation of hydroxyl compounds and their regeneration in the presence of inexpensive and bench-top catalysts. Water is the ideal green solvent for many mild catalytic transformations from both economical and environmental perspectives.…”