Lithium, organo-, compounds basicity

Table 13.4 allows for a comparison of the basicities of the strongest lithium-containing bases. The basicities are measured by the heats of deprotonation liberated upon mixing the reference acid isopropanol with these bases. These heats of deprotonation reveal that organo-lithium compounds are even stronger bases than lithium amides. Their basicities decrease from te/7-BuLi via. sec-BuLi and w-BuLi to PhLi. 

Oxetanes are rather basic materials and are inert to attack by bases. However, as stated above, anionic polymerization of thietanes has been reported [67], Significantly, in anionic polymerizations initiated by organo-lithium compounds the propagating end is a carbanion rather than a thiolate species viz. 

These methods of acylation are devices to solve the problem that acid chlorides and organo-lithium or magnesium derivatives are not good partners. To get good acylation with acid chlorides, as well as good alkylation with alkyl halides, we need to turn to other metals which provide softer carbanion complexes, less basic compounds with metals showing a lower affinity for oxygen. The most important is copper. 

Like their aryl and alkenyl counterparts, alkynylboronic adds can be made by displacement of magnesium or lithium acetylides with borate esters. For example, Mat-teson and Peacock have described the preparation of dibutyl acetyleneboronate from ethynylmagnesium bromide and trimethyl borate [294]. The C-B hnkage is stable in neutral or acidic hydrolytic solvents but readily hydrolyzes in basic media such as aqueous sodium bicarbonate. Brown and co-workers eventually applied their organo-lithium route to boronic esters to the particular case of alkynylboronic esters, and in this way provided a fairly general access to this class of compounds [295]. 

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