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A wide variety of oxathioacetals 1 as well as dithioacetals 2 can be chemoselectively deprotected to the corresponding carbonyl compounds 3 in good yields by employing NaNO 2 -AcCl and H 2 O in CH 2 Cl 2 at 0°C to room temperature. Some of the major advantages of this procedure are: mild conditions, easy to handle, highly chemoselective and efficient, high yields and inexpensive reagents. In addition, no acetylation occurs at the hydroxyl group nor chlorination takes place at the double bond.The protection-deprotection strategy is a common practice in multistep organic synthesis. Among the various functional groups, protection of carbonyl groups as oxathioacetals and dithioacetals has attracted much attention due to their robustness under mild acidic or basic reaction conditions. They also serve as acyl carbanion equivalents for carbon-carbon bond forming reactions. 1 The most remarkable application is the use of chiral oxathioacetals for the synthesis of optically active tertiary alcohols possessing a carbonyl functionality at the α-position, first demonstrated by Eliel and Lynch. 2 Later on, the utility of oxathioacetals was further shown by Utimoto and his group in organic synthesis. 3 In contrast to many methods available for deprotection of dithioacetals, a few methods are known for oxathioacetals. 4 Consequently, there is a need to find out a better alternative for deprotection of oxathioacetals, which might work under mild conditions. The existing procedures for the deprotection of oxathioacetals are as follows: i) use of isoamyl nitrite 5a and chloramine T, 5b ii) treatment with TMSOTf alone, 6a iii) or with TMSOTf in the presence of p-nitrobenzaldehyde, 6b,c or polymer supported p-nitro-benzaldehyde, 6d iv) use of halonium ion sources in the presence of expensive silver salts 7 or reaction with NBS in acetone. 8 Unfortunately, some of the procedures have serious drawbacks such as the removal of the by-product oxathioacetal derived from p-nitrobenzaldehyde 6b,c or the use of an expensive polymer supported reagent 6d and sometimes failure to deprotect non-benzylic oxathioacetals. 6a They also require long reaction times. 6d Other drawbacks related to halonium ion sources include the need for a large excess in expensive reagents such as silver salts 7 and require long reaction times. 8 Recently, another method was reported 9 by Kirihara et al. using a catalytic amount of trichloroxyvanadium, which also requires drastic reaction conditions. We have also demonstrated some new methodologies based on bromonium ion sources for deprotection of various oxathioacetals 10a-c and dithioacetals, 10d-f which involve expensive organic ammonium tribromides 10b,e and require relatively long reaction times. Very recently one more method was reported 11 using CeCl 3 ⋅7H 2 O-NaI, which require long reaction times as well as expensive reagents. Though a large number of methods have already been reported in the literature 12 for deprotection of dithioacetals to the corresponding carbonyl compounds, still there is a need to de...

The oxidative coupling of the α‐carbon atom of aromatic ketones with unactivated arenes in the presence of selenium dioxide and p‐toluenesulfonic acid monohydrate is described. A number of unsymmetrical benzils have been prepared in good yields (38–75 %) with high regioselectivity. The generality and functional tolerance of this new protocol is demonstrated. The mechanistic pathway for the oxidative coupling reaction is also described. The reaction displays superiority in terms of minimization of steps with the C–C bond formation promoted by SeO2 and pTsOH·H2O. This method is advantageous as the reactants used as the solvent can be recovered.

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A wide variety of thioacetals and thioketals can be cleaved chemoselectively in presence of olefin and aromatic ring as well as other protecting groups to carbonyl compounds by employing V2O5 catalyzed oxidation of ammonium bromide by H2O2 in CH2Cl2–H2O solvent system; mild conditions, high selectivity, good yield, and no side products such as bromination or oxidation are some of the major advantages.