Interconversion of oxathiolanes and carbonyls under essentially identical conditions

Nickel(II) chloride hexahydrate catalyzed reaction of aromatic aldehydes with 2-mercaptoethanol: formation of supramolecular helical assemblage of the product

“…OEt 2 6 and ZnCl 2 . 7 Recently some more methods have also been reported in the literature for the protection of the carbonyl groups as 1,3-oxathiolanes by utilizing various catalysts, viz ZrCl 4 , 8 TMSOTf, 9 TIPSOTf, 10 OATB, 11a BDMS, 11b HClO 4 -SiO 2 , 11c LiBF 4 , 12 NBS, 13 TBAB,14 Sc(OTf) 3 , 15 In(OTf) 3 , 16 Pr(OTf) 4 , 17a and Y(OTf) 4 . 17b Some of them have some drawbacks like prolonged reaction time and poor yields, 6,7 requirement of an expensive metal triflate catalyst, [15][16][17] high catalyst loading, 6,7,13 and use of volatile organic solvents namely acetonitrile and dichloromethane.…”

“…It is well-known that the reaction of aromatic aldehydes with 2-mercaptoethanol usually gives 1,3-oxathiolane derivatives (4) as the sole product using different catalysts. [6][7][8][9][10][11][12][13][14][15][16][17] It was found in the literature that only a few methods are known for unusual product formation using SiO 2 -NaHSO 4 19 , Ce(OTf) 3,20 and TMSCl 21 as catalysts. In 2006, we have demonstrated the protection of various carbonyl compounds as 1,3-oxathiolane derivatives (4) using silica supported perchloric acid.…”

A highly efficient procedure for the oxathioacetalization of carbonyl compounds under solvent-free conditions

“…O/S-acetals and ketals are generally prepared from carbonyl compounds in the presence of acid catalysts [5] . The commonly used catalysts are protonic acids, Lewis acids, transitional metal complexes including TMSOTf, ZrCl 4 , LiBF 4 , HClO 4 , Sc(OTf) 3 , In(OTf) 3 , PTSA, BF 3 -OEt 2 , ZnCl 2 , TMSCl-NaI, TMSOTf, AlCl 3 , TiCl 4 , LaCl 3 , LiClO 4 / Et 2 O(LPDE) and TaCl 5 /SiO 2 [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] . Although some of these methods have convenient protocols with moderate to high yields, the majority of these methods suffer at least from one of the following disadvantages: reactions under oxidizing conditions, use of halogenated solvents, high temperature, long reaction time, moisture sensitivity of the catalyst, high cost and high toxicity.…”

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].…”