High Reactivity and Extremely Easy Synthesis

Cyclometalation reactions for the synthesis of organometallic intramolecular-coordination five-membered ring compounds proceed very promptly, because hve-membered ring compounds are more stable as compared with other ring compounds, such as four- and six-membered ring compounds. The cyclometalation reactions generally proceed regioselectively as a result. 

The selectivity of hve-membered ring compounds is recognizable in all cyclometalation reactions, as shown in Table 5.1 [1]. The mean selectivity ratio shown in the tables is approximately 80 %. For organotin compounds, however, the ratio of five-membered ring compounds increases to approximately 85 %, as shown in Table 5.2 [2]. Furthermore, the selectivity of reactions of halo-carbonyl compounds with tin (see Eq. (2.2)) is 95 %, as shown in Table 5.3 [1]. 

The high reactivity is also understandable from the mild reaction conditions under which many cyclometalation reactions proceed with many kinds of metal elements, such as Ti, Fe, Ru, Os, Rh, Ir, Ni, Pd, Pt, B, and Cu, and with many kinds of substrates, such as amines, imines, 2-phenylpyridines, benzo[/ ]quinones, quinolines, diarylpyridines, naphthyridines, azobenzenes, oxazolines, aldehydes, ketones, amides, phosphines, phosphites, and alkyl sulfides, as shown in Figs. 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, and 5.9. 

Four-membered ring Five-membered ring Six-membered ring 

The 2008 version of the CSD contained 456,637 entries Subsequently added articles numbered 12,801 in May 2009 

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Grignard reagents have proved to be extremely powerful synthetic tools because of their easy accessibility and high reactivity they enable the nucleophilic introduction of organic groups as carbanion equivalents and for that reason are in standard repertoires for both organic and organometallic synthesis. 

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