A First Example Using o-Iodoxybenzoic Acid (IBX) in Combination with Tetraethylammonium Bromide (TEAB) for Ring Expansion of 1,3-Dithiolanes and 1,3-Dithianes

Abstract

A novel one-pot procedure for the synthesis of dihydro-1,4-dithiins and dihydro-1,4-dithiepines from the corresponding 1,3-dithiolanes and 1,3-dithianes using o-iodoxybenzoic acid (IBX) in combination with tetraethylammonium bromide (TEAB) is described. The salient features of the protocol include mild reaction conditions, short reaction times and high yields.

o-iodoxybenzoic acid (IBX) - dithiins - dithiepines - ­tetraethylammonium bromide (TEAB)

References

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14

General Experimental Procedure.
To a stirred suspension of IBX (1.1 equiv) in 10 mL dry CHCl₃ was added TEAB (1.1 equiv) in one portion. The mixture was stirred at r.t. for 5 min followed by the addition of 1,3-dithiolane/1,3-dithiane (1.0 equiv) and stirring continued at r.t. until complete consumption of starting material as observed by TLC. The reaction mixture was diluted with CHCl₃ and the organic layer was washed successively with 10% Na₂S₂O₅ solution (2 × 15 mL), sat. NaHCO₃ solution (2 × 15 mL), H₂O (2 × 15 mL), and brine (1 × 15 mL). The organic layer was dried over Na₂SO₄ and concentrated in vacuo. Purification by silica gel column chromatography (10% EtOAc-hexane) afforded the pure dihydro-1,4-dithiins and dihydro-1,4-dithianes.