Nickel(II) chloride as an efficient and useful catalyst for chemoselective thioacetalization of aldehydes

Poly(N-bromoacrylamide): an efficient and useful catalyst for the protection of carbonyl compounds as dithiolanes, dithianes and oxathiolanes under solvent-free and microwave conditions

“…Recently, methods employing catalysts such as N-bromosuccinimide [4,5], *Corresponding author. E-mail: tamami@chem.susc.ac.ir tricholoro isocyanoric acid [6], I 2 [7], AlCl 3 -SiO 2 [8], NaHSO 4 -SiO 2 [9], PPA-SiO 2 [10], silica chloride [11], p-TsOH-silica gel [12], montimorillonite K-10 [13], H 3 PW 12 O 40 /SiO 2 [14], LiBF 4 [15], MoO 2 (acac) 2 [16], SnCl 2 .2H 2 O [17], Bi(NO 3 ) 3 [18], ScCl 3 [19], NiCl 2 [20], InCl 3 [21,] ZrCl 4 [22], WCl 6 [23], LiBr [24], Y(OTf) 3 [25], VO(OTf) 2 [26], Sc(OTf) 3 [27,28] have also been reported in the literature. However, many of these procedures are associated with certain limitations such as low yields, harsh reaction conditions, difficulties in work-up, requirement for an inert atmosphere, use of stoichiometric reagents, sensitivity to moisture, long reaction times, cost, and inconvenience in handling the reagents or catalysts.…”

A Vicinal Acyloxy Group Participation SN2 Reaction of Thiol Nucleophiles in the Formation of Thioacetals

“…Usually, they are prepared via the condensation of carbonyl compounds with thiols in the presence of protic acids or Lewis acids, such as ZnCl 2 , 3 NiCl 2 , 4 InCl 3 , 5 I 2 , 6 NBS 7 and SiO 2 -SO 3 H. 8 Herein, we wish to report a vicinal acyloxy group participation S N 2 reaction of ethanethiol under the standard thioacetalization conditions.…”

Selective Protection of Carbonyl Compounds over Nano-sized Nickel Catalysts

“…This 'umpolung' or inversion of polarity is an integral step of many multistep organic syntheses. Several methods for the preparation of thioacetals, dithiolanes, or dithianes derivatives from carbonyl compounds such as p-TsOH [4] in refluxing benzene (removing the water as an azeotrope with benzene), BF 3 -OEt 2 [5], ZnCl 2 [6], SO 2 [7], TMSCl-NaI [8], TMSOTf [9], AlCl 3 [10], TiCl 4 [11], Cu(OTf) 2 -SiO 2 [12], SOCl 2 -SiO 2 [13], ZrCl 4 -SiO 2 [14], NiCl 2 [15], Bi(NO 3 ) 3 [16], Bi(OTf) 3 [17], LiBr [18], LiBF 4 [19], InCl 3 [20], molecular I 2 [21], 5 M LiClO 4 [22] have been reported. Although some of these methods have been carried out under mild reaction conditions, most of them require [7,13] reflux temperature [4,17], long reaction times and use expensive and not readily available reagents [17].…”