Organometallic donors

Such processes have been recognized when the donor organometallic, R—M, is a radical anion, a dianion, an alkyllithium reagent, or a Grignard reagent (113, 71, 70, 59, 114). In most cases, the anion radical... 

Many hydride donors, organometallic compounds, and heteroatom-stabilized carbanions react with carboxylic acids and their derivatives. However, the corresponding substitution... 

SN Reactions of Hydride Donors, Organometallics, and Heteroatom- Stabilized Carbanions on the Carboxyl Carbon... 

Most SN reactions of hydride donors, organometallic compounds, and heteroatom-stabi-lized carbanions at the carboxyl carbon follow the mechanism shown in Figure 6.2. Thus, the substitution products, i.e., the aldehydes and ketones C, form in the presence of the nucleophiles. Thus, when the nucleophile and the acylating agent are used in a 2 1 ratio, alcohols F are always produced. 

Fig. 6.40. On the chemo-selectivity of the reactions of hydride donors, organometallic compounds, and heteroatom-stabilized "carbanions with acylating agents (kM t refers to the rate constant of the addition of the nucleophile to the carboxyl carbon, and kadd2 refers to the rate constant of the addition of the nucleophile to the carbonyl carbon).

For the reaction of hydride donors, organometallic compounds and heteroatom-stabilized carbanions with acylating agents or carbonyl compounds one encounters a universal reactivity order RC(=0)C1 > RC(=0)H > R2C=0 > RC(=0)0R > RC C NR It applies to both good and poor nucleophiles, but—in agreement with the reactivity/selectivity principle (Section 1.7.4)—the reactivity differences are far larger for poor nucleophiles. 

Fig. 6.41. Three strategies for the chemoselective acylation of hydride donors, organometallics and heteroatom-stabilized "carbanions" with carboxylic acid derivatives.

The SN reaction under consideration is not terminated until water, a dilute acid, or a dilute base is added to the crude reaction mixture. The tetrahedral intermediate B is then protonated to give the compound E. Through an El elimination it liberates the carbonyl compound C (cf. discussion of Figure 6.4). Fortunately, at this point in time no overreaction of this aldehyde with the nucleophile can take place because the nucleophile has been destroyed during the aqueous workup by protonation or hydrolysis. In Figure 6.32 this process for chemoselective acylation of hydride donors, organometallic compounds, and heteroatom-stabilized carbanions has been included as strategy 1. ... 

Xu, X., Xu, X.Y., Chen, YF. etal. (2008) Dialkyllanthanide complexes containing new tridentate monoanionic ligands with nitrogen donors. Organometallics, 27, 758. 

Schick S, Pape T, Hahn FE. Coordination chemistry of bidentate bis(NHC) bgands with two different NHC donors. Organometallics. 2014 33 4035 041. 

Containing Donors Organometallic Donors No Donating Moiety... 

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