Synthesis of Thiols RSH and Thioethers RSR

While the retrosynthesis of a thioether should still take into consideration the more favorable, less hindered Sn2 mechanism, it is possible to do a backside attack of RS on a secondary alkyl halide to synthesize a sterically crowded thioether. A symmetrical thioether or cyclic ether can be prepared via sequential Sn2 displacements of two halides with sodium sulfide (Na2S). 

Introduction to Strategies for Organic Synthesis, First Edition. Laurie S. Starkey. 2012 John Wiley Sons, Inc. Published 2012 by John Wiley Sons, Inc. 

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