Heterogeneous Thiocyanation of Benzylic Alcohols and Silyl and THP Ethers, and Deprotection of Silyl and THP-Ethers by [PCl_3-n(SiO₂)_n] (Silphos)

Abstract

Silicaphosphite (silphos), [PCl_3-n(SiO₂)_n], as a heterogeneous phosphorous compound, catalyzes the thiocyanation of benzylic alcohols and silyl and THP ethers in the presence of I₂ and NH₄SCN in refluxing CH₃CN. The produced silphos oxide byproduct can be easily separated by a simple filtration. Silphos is also used for the efficient and selective deprotection of silyl and THP-ethers to their corresponding alcohols.

KEYWORDS:

• Alcohol
• deprotection
• silyl ether, silphos
• thiocyanation
• THP-ether

Notes

^a Conversion yield is based on GC analysis using n-octane as internal standard.

^a GC and NMR yield using n-octane as internal standard.

^b Yield% of thiocyanates and isothiocyanates were determined by NMR analysis.

^c Gc yield.

^d The reaction was done with 2 equivalents of silphos.

^e All the products are known compounds and were identified by comparison of their physical and spectral data with those of authentic samples. ^{1 , 2}

^a GC yield using n-octane as internal standard.

^b Reflux condition.