Mono-Deuteration of Bis ethylthio methane

H2C(SC2H5)2 + BuLi h+7 e LiCH(SC2H5)2 + C4H10 LiCH(SC2H5)2 + D20----- DCH(SC2H5)2 + LiOD j 

Deuterated compounds may be needed for mechanistic or physical studies and a very high purity (i.e., preferably at least 97% of the product should consist of the compound having the D-atom on the desired place) is often necessary. A general method consists in treating the alkali-metal derivative with deuterium oxide or deuteriomethanol or -ethanol. The presence of undeuterated compound may be due to incomplete metallation, therefore this reaction is carried out with an excess of the basic reagent. This involves, however, some risk of introduction of more than one D-atom, especially when the quench operation is not conducted in the proper way  

A good procedure for the preparation of 2-phenyl-l,3-dithiane-2-d is described by Seebach D, Erickson BW, Singh G (1966) J Org Chem 31 4303 

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