Tetrahydropyranylation of Alcohols Under Solvent-Free Conditions

Abstract

A green, efficient, and large-scale method for tetrahydropyranylation of alcohols in the presence of a catalytic amount of pyridinium chloride at room temperature under solvent-free conditions is reported.

Sulfonic acid-functionalized ordered nanoporous Na+-montmorillonite (SANM) as an efficient and recyclable catalyst for the tetrahydropyranylation and detetrahydropyranylation of alcohols and phenols

“…Primary and secondary aliphatic alcohols were also efficiently converted to their corresponding products under the same reaction conditions ( Table 2, entries [17][18][19][20]. This method was found to be useful for the protection of hindered secondary and tertiary alcohols, and isomerization and dehydration of these compounds were not observed ( Table 2, entries 19-21).…”

“…A wide variety of catalysts such as Sn IV (TPP)(OTf) 2 [2], polystyrene-supported GaCl 3 [3], silica sulfuric acid [4], solid silica based sulfuric acid [5], melamine trisulfonic acid [6], CuSO 4 Á5H 2 O [7], acetic acid assisted copper o-toluenesulfonate [8], Fe(ClO 4 ) 3 [9], Al(OTf) 3 [10], Sn IV (TNH 2 PP)(OTf) 2 @CMP [11], Al/AT-silica [12], {[K.18-crown-6]Br 3 } n [13], NbCl 5 [14], La(NO 3 [20] have been applied for tetrahydropyranylation of alcohols and phenols. However, many of these methods suffer from disadvantages such as long reaction times [9,10], unsatisfactory yields, harsh reaction conditions [8], expensive reagents [11,13,19], hazardous and toxic solvents or catalysts [17,18], tedious work-up, formation of polymeric by-products of the dihydropyran (DHP) and isomerization.…”

β-Cyclodextrin in water: highly facile biomimetic one pot deprotection of phenolic THP/MOM/Ac/Ts ethers and concomitant regioselective cyclization of chalcone epoxides and 2′-aminochalcones

“…2 Likewise, methoxymethyl chloride (MOMCl), acetyl chloride/acetic anhydride (CH 3 COCl/Ac 2 O) and tosyl chloride (TsCl) are also important reagents for the alcoholic and phenolic group protection. Various methods have been reported for the deprotection of THPEs that include protic acids, 3a- CBr 4 -PPh 3 , 4f ZnBr 2 , 4g silica-supported NaHSO 4 , 4h and TMSOTf (TESOTf)-2,2'-bipyridyl.…”

SnCl4 or TiCl4: highly efficient catalysts for the detetrahydropyranylation and demethoxymethylation of phenolic ethers and sequential one-pot asymmetric synthesis of 3-aryl-2-hydroxy-2,3-dihydroindan-1-ones from chalcone epoxides

“…2,3 Conversely, the deprotection of the THP and MOM ethers requires efficient methods to avoid the decomposition and/or loss of other functional groups in the product under harsh reaction conditions. In particular, the protection and deprotection of hydroxyl groups are extremely important because of their enormous demand for the synthesis of a number of compounds of biological and synthetic interest such as carbohydrates, macrolides, peptides, steroids, nucleotides and polyethers.…”