Inert atmospheres nitrogen inerting improves yields

In the presence of TMS-Cl the enediolate dianion and, importantly, the alkoxide ions, are trapped as their neutral silyl ethers (Scheme 5). This leads to much improved yields of the coupled product the acyloin is isolated in the form of its silyl enediol ether (3). Work-up is much easier. It is only necessary to filter the solution, evaporate the solvent, and isolate the product by distillation or chromatography. The TMS-Cl should be purified by distillation from calcium hydride, under a nitrogen or argon atmosphere, before use. A convenient procedure when using an organic solvent is to add the ester and the TMS-Cl together, dropwise, to the alkali metal finely dispersed in the solvent, at a rate sufficient to maintain the reaction. An explosion has been reported where this procedure was not followed. For a reaction conducted in liquid ammonia the TMS-Cl is added at the end of the reaction and after all the ammonia has been allowed to evaporate. Particularly in cases where sodium-potassium alloy has been used, a pyrophoric residue may have formed, so that the filtration must be carried out under an inert atmosphere. 

In the first papers published in 1988, the detonation of explosives was carried out in inert gases, such as CO2 and nitrogen, used as the protective atmosphere and cooling agent. The yield was ratlier low and tire production method was ratiier complex and not suitable for mass production. Since then, much attention has been paid to improvement of the preparation method. 

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