Reductive Dehalogenation of a-Haloketones by Sodium Borohydride and Tin(II) Chloride in Tetrahydrofuran

The dehalogenation of a-haloketones and a-halocarbonyl compounds is an inevitable proce­ dure for the organic synthesis and these reductive dehalogenations have been often effected in organic syntheses. There have been various procedures for the purpose and these are obtained by zinc and acetic acid [1], sodium dithionite [2], titanium(III) chloride [3], organotin hydride [4], sodium hydrogen telluride [5], sodium iodide and sulfuric acid [6], sodium iodide trimethyl-chlorosilane [7], lithium iodide and boron trifluoride [8], cerium iodide [9], and iodotrimethylsilane [10] etc. On the other hand, Ho pro­ posed hard soft acid and base principle [11 — 13] (H SA B ) for organic reaction [13], applied the princi­ ple to the reductive dehalogenation of a-haloketones [9 , 10], and represented the reaction mechanism. The authors have been interested in the reduction of organic compounds by sodium borohydride and metal salts and found that the reduction of ketonic carbonyl by sodium borohydride in tetrahydrofuran is suppressed by addition of tin(II) chloride. a-Halocarbonyl compounds are successfully dehalogenated to their corresponding parent carbonyl compounds by sodium borohydride and tin(II) chloride. The successful results are reported.