Aroyllithiums

Acyl- and aroyllithiums are generated by submitting telluroesters, easily accessible from the corresponding acid chlorides and tellurolate anions (see Section 3.11), to the above-described lithium-tellurium exchange reactions. ... 

Negatively charged carbonyl species, which are referred to as carbonyl anions (e.g. acyl- and aroyllithium derivatives), represent one of the more reactive organic intermediates that heretofore has rarely been utilized in practical synthetic reactions [1]. The carbonyl anion is a strong nucleophile, and at the same time it is an electrophile since it has a carbonyl function which is electrophilic in nature. Therefore, reactions involving a carbonyl anion are not straightforward, and usually a complex mixture is obtained from a reaction. 

Generation of Acyl-and Aroyllithiums via Lithium-Tellurium Exchange. . . 132... 

Seyferth and co-workers reported the nucleophilic acylation of carbon electrophiles such as aldehydes [13a],ketones [13a,b],esters[13a,b],lactones [13c], and trialkylchlorosilanes [13d] with acyl- and aroyllithiums generated in situ from the RLi/CO system at very low temperatures (-110 °C to -135 °C). They have also applied this system to the acylation of disulfides, as shown in Eq.8 [14]. 

The most straightforward method for nucleophilic introduction of acyl and aroyl groups into organic molecules is the use of carbonyl anions, represented by acyl-and aroyllithiums, as nucleophiles. Their synthetic utility, however, has been severely limited for a long time because of difficulties both in their generation and in controlling their reaction courses. A practically useful route to acyl- and aroyllithiums has been developed, based on the efficient lithium-tellurium exchange of tellurol esters [123]. 

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