Ultrasonic acceleration lithium

Reactions involving lithium appear to be particularly good candidates for ultrasonic acceleration. The reduction of some highly unsaturated cyclic hydrocarbons by lithium was not only accelerated but pushed to completion by ultrasonic irradiation(19) ... 

General. Ultrasonic acceleration of the formation of organollthlums using metallic lithium has been further illustrated o-LiCHgCgH CHgBr, Anth, 2Li, ... 

Halides of the less electropositive metals are quickly reduced to highly dispersed and very active metal powders if they are exposed to ultrasonic waves in the presence of lithium and other group I metals(20). Ultrasound not only accelerates the reduction of the halides but also increases the rate of subsequent reactions of these less active metals. These reactions are covered in the chapter by K. Suslick. 

The ultrasonic preparation of thioamides from amides and phosphorus pentasulfide by Raucher(51) and of dichlorocarbene from chloroform and potassium hydroxide by Regen(52) are some of the more recent examples of nonmetallie applications. We were surprised to find that ultrasound greatly accelerates the reduction of haloaroma-tics by lithium aluminum hydride, permitting the reaction to be... 

In many syntheses activation is not effected by sonochemical preparation of the metal alone but rather by sonication of a mixture of the metal and an organic reagent(s). The first example was published many years ago by Renaud, who reported the beneficial role of sonication in the preparation of organo-lithium, magnesium, and mercury compounds [86]. For many years, these important findings were not followed up but nowadays this approach is very common in sonochemistry. In another early example an ultrasonic probe (25 kHz) was used to accelerate the preparation of radical anions [87]. Unusually for this synthesis of benzoquinoline sodium species (5) the metal was used in the form of a cube attached to the horn and preparation times in diethyl ether were reduced from 48 h (reflux using sodium wire) to 45 min using ultrasound. 

Preparative Methods made by addition of freshly cut Lithium metal to a solution of naphthalene in THF. Preparation can be accelerated by ultrasonication. ... 

Effects of Sonication. In a subsequent study [92] on the accelerating effect of ultrasonic waves on the Barbier reaction of benzaldehyde, 1-bromo-heptane and lithium, Luche and co-workers could not state that cavitation was the only important phenomenon. No information had been obtained on the effects of non-cavitational shock waves or the frequency. The authors came to the conclusion that the work published had to be considered as an approach for a better knowledge of the interaction of ultrasound with a heterogeneous system, but the problem in its generality could not be considered as fully understood. 

---