A facile and efficient ZrCl 4 catalyzed conversion of aldehydes to geminal-diacetates and dipivalates and their cleavage

Chemoselective Protection and Deprotection of Aldehydes Using Solid Supported Reagent (Silica Chloride) Under Solvent-Free Conditions

“…[29] Although these are convenient procedures and give high yields of the desired products, they suffer from one or more drawbacks such as longer reaction time, highly corrosive nature, they involve expensive catalysts, and use solvents. The deprotection of acylals, on the other hand, has also been reported using some of the protic acids such as H 2 SO 4 , [21] BiCl 3 , [30] Sc(OTf) 3 , [31] CAN, [17] ZrCl 4 , [32] and CBr 4 . [33] Most of them are corrosive, expensive, or non-reusable catalysts; hence, developing a more efficient, economical, and greener protocol is still required.…”

H-Mordenite zeolite as an efficient, rapid and recyclable catalyst for chemoselective synthesis o

“…Various methods have been reported in the literature for the synthesis of 1, 1-diacetate from strong acids including sulfamic acids [5], sulphuric acid [6], methane sulphuric acid [7] lewis acids such as lithium bromide [8], FeCl3 [9], PCl3 [10], NBS [11], expensive graphite [12], zeolite HSZ-360 [13], montmorillonite clay [14], Sulphate Zirconia [15], Cu(OTf)2 [16], Sc(OTf)3 [17], and ZrCl4 [18], P2O5 [19], sodium lithium perchlorate [20] [24], aluminum chloride [25], and certain transition metal compounds and complexes [26] which are more effective for this conversion. However, above these methods have some main limitations such as formation of low yield, long reaction time, high temperature, strong acidic condition, expensive reagents, corrosive and highly toxicity.…”

Silica immobilized sulfuric acid ([3-(propyl)sulfanyl]propyl]ester andN-propylsulfamic acid as recyclable catalysts for chemoselective synthesis of 1,1-diacetates

“…Appropriate nucleophiles can convert the acylal functionality into other functional groups (8,9). Generally, they are synthesized from acetic anhydride and aldehydes using strong protonic acids as catalysts, such as sulfuric (10), phosphoric (11), methanesulfuric (12), or perchloric acid (13), Lewis acids, such as FeCl 3 (2), PCl 3 (14), InCl 3 (15), ZrCl 4 (16) (23), Cu(OTf) 2 (24), Sc(OTf) 3 (25), LiOTf (26), and heterogeneous catalysts such as Nafion-H (27), expansive graphite (28), zeolites (29), montmorillonite clay (30,31), and supported reagents (32Á35). Other catalysts, such as iodine (36), N-bromosuccinimide (37), and trimethylchlorosilane/sodium iodide (38), have also been used for this transformation, but these procedures are often accompanied by longer reaction times, poor product yields, stringent conditions, good catalyst loading; require the use of toxic solvents; and so on.…”