Ecofriendly Solid-State Oxidative Deprotection of 1,3-Dithianes and 1,3-Dithiolanes Using Ammonium Persulfate on Wet Montmorillonite K-10 Clay Support under Microwave Irradiation

Abstract

Solid-state microwave-assisted oxidative deprotection of 1,3-dithianes and 1,3-dithiolanes of aromatic aldehydes and ketones, cyclic ketones, α,β-unsaturated aldehydes and aliphatic aldehydes and ketones has been accomplished using ammonium persulfate on wet montmorillonite K-10 clay support.

Key words

ammonium persulfate - cleavage - 1,3-dithianes - 1,3-dithiolanes - microwave - montmorillonite K-10 clay

References

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31

Representative Procedure for the Deprotection of 1,3-Dithianes and -1,3-Dithiolanes under Solvent-Free Conditions. 2,2-Diphenyl-1,3-dithiane (330 mg, 1.2 mmol) was dissolved in the minimum amount of CH₂Cl₂ (1.5 mL) and to it was added montmorillonite K-10 clay (0.4 g). Removal of volatiles in vacuo gave a free-flowing powder. A concentrated solution of ammonium persulfate (1.64 g, 7.2 mmol) in H₂O (0.3 mL) was separately adsorbed on montmorillonite K-10 clay (0.6 g). It was thoroughly mixed with the free-flowing powder and the mixture was irradiated at 300 W power level for 2 min (TLC-monitored) in a conical flask. The cooled reaction mixture was extracted with CH₂Cl₂ (3 × 15 mL) and the clay was removed via filtration through a sintered glass funnel. Careful concentration of the combined organic extracts under H₂O suction gave the crude product showing a single TLC spot. Chromatographic filtration over silica gel (60-120 mesh) using light petrol (40-60 °C) as the eluant afforded benzophenone, mp 47-48 °C (200 mg, 90%). It was found to be identical with an authentic sample of benzophenone in all respects.