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DOI: 10.1055/sos-SD-026-00532

Landais, Y.; Vincent, J. M.Science of Synthesis, (200526649.

The choice between the different coupling methods relies upon the availability of the precursors, the versatility of the method in terms of functionalities allowed within the 1,2-diketone skeleton, and finally, on the nature of the desired 1,2-diketones. Several methods provide only symmetrical 1,2-diketones, as is the case with coupling of carboxylic acid derivatives (Section Apart from one useful exception using tin precursors, methods using coupling reactions are not suitable for the preparation of unsymmetrical 1,2-diketones. However, coupling reactions involve inexpensive and readily available precursors, which explains the efforts in developing this approach. Similarly, the FriedelCrafts reaction (Section is restricted to the preparation of symmetrical aromatic 1,2-diketones. Addition of organometallic reagents to 1,2-diacyl derivatives (Section is, in most cases, restricted to the preparation of symmetrical diketones and, in this case, the methods in Sections and are preferred due to their simplicity. However, one variation using cyclic 1,2-diamides provides unsymmetrical 1,2-diketones in good yields (see Section The restriction in applying the addition of organometallic reagents to 1,2-diacyl derivatives results from the low level of functionality, that is, when using Grignard and organolithium reagents. Carbonylative coupling of alkyl halides and nucleophilic acylation with acyllithium reagents (Sections and are convergent methods that provide access to both symmetrical and unsymmetrical alkyl- and aryl-substituted 1,2-diketones. However, these methods require an inert atmosphere and precursors that are not always readily available. As for other methods, functionalities may be difficult to introduce using such highly reactive intermediates.