Development of a New Heterogeneous Lewis Acid Catalyst for Chemoselective Tetrahydropyranylation of Different Hydroxyl Compounds

Abstract

Amino functionalized triazine supported on silica-gel was prepared and characterized. This new triazine derivative was applied as a coordinating agent for aluminum chloride. This novel Lewis acid supported on heterogeneous surface was used as an effective catalyst for protection of alcohols and phenols in the presence of 3,4-dihydro-2H-pyran. This catalyst can be reused without any significant loss of activity, and it protects alcohols in the presence of phenols.

Highly Active and Efficient Cu@SiO2 Catalyst: Enabled Nucleophilic and Electrophilic Activation of Active Methylene Compounds

“…The Cu nanoparticles are found to have an average of 2.5 nm in size. The synthesized solid material selected the different zones to find out the lattice fringes of Cu on the SiO 2 surface see Figure 3 A and interplanar spacing value of 0.25 nm, corresponding to the (1 1 0) plane, which is corroborated with XRD d‐spacing value (JCPDS 00‐005‐0667) [33,39,42,56] …”

“…The band at 1088 and 818 indicates Si−O−Si and Si−OH asymmetric stretching vibration. The presence of a band at 462 cm −1 corresponds to the bending vibrations of Cu‐OH groups present in Cu@SiO 2 [39–53] . The scanning electron microscopy (FE‐SEM) analysis depicted in Figure 2 compares the morphological topography of SiO 2 and 4 wt % Cu@SiO 2 catalyst.…”

“…The presence of a band at 462 cm À 1 corresponds to the bending vibrations of Cu-OH groups present in Cu@SiO 2 . [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] The scanning electron microscopy (FE-SEM) analysis depicted in Figure 2 compares the morphological topography of SiO 2 and 4 wt % Cu@SiO 2 catalyst. Due to the excess use of ammonia, the reaction medium becomes basic, and under such conditions, the gel particles tend to make Stöber silica particles appear spherical-shaped (Figure 2(A).…”

“…Unequivocally, the catalyst possesses versatile application in organic transformation. Considering this, our interest is to utilize various AMCs to synthesize high‐value chemicals [39–63] . Herein, we demonstrated that Cu@SiO 2 enabled Knoevenagel condensation, followed by Michael's addition of AMC on carbonyl, halides, and coupling with amines towards Gabapentin intermediates.…”

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

“…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.…”