Bonding nucleophilic attack

Figure 22.13 shows the scheme used to describe the hydroformylation process. The active catalyst is HCo(CO)3, which is a 16-electron species that is coordinatively unsaturated. After that species is generated, the first step of the catalyzed process involves the addition of the alkene to the catalyst. In the next step, an insertion reaction occurs in which the alkene is inserted in the Co-H bond (nucleophilic attack by H on the alkene would accomplish the same result as described... 

Electrooxidation of a-alkoxystannanes on a preparative scale can therefore be carried out at lower potentials, with cleavage of the C—Sn bond. Nucleophilic attack, e.g. by methanol, butanol or an amine on carbon at that a position, gives the product in high yields, 90-95% diether or 55% aminoether. A number of examples have been given ... 

Molecular modeling of the reaction predicts attack of the CN" ion on the re face of the iV-allyl benzaldimine carbon to provide an (5)-adduct. The aromatic ring of the imine and the quinuclidine hydrogen bond stabilizes the iminium above the pyridazine, blocking the rear face of the imine bond. Nucleophilic attack by CN is... 

Vinylation of dienes in the presence of piperidine or morpholine yields aminodienes as major products. Sometimes trienes are minor products. The reaction is believed to proceed by way of a ir-allylpal-ladium complex formed by addition of the vinylpalladium halide to the least-substituted diene double bond. Nucleophilic attack of the amine upon the ir-allylic complex gives the aminodienes, while hydridopalladium halide elimination yields trienes (Scheme 6).97... 

Palladium coordinates to one face of the diene promoting intramolecular attack by the alcohol on the opposite face. The resulting <7-alkyl palladium can form a 71-allyl complex with the palladium on the lower face simply by sliding along to interact with the double bond. Nucleophilic attack of chloride from the lithium salt then proceeds in the usual way on the face opposite palladium. The overall addition to the diene is therefore cis. 

Palladium(II) catalysts have been found to be more effective than platinum(II), presumably owing to the lesser stability of the olefin complexes of the former resulting from minimized back-bonding in palladium. By reducing the electron density around the double bond, nucleophilic attack on the double bond is facilitated. 

Figures. Thiol-thioester exchange to form an amide bond. Nucleophilic attack takes place by the side chain thiol functionality in a cysteinyl peptide at a thioester segment to form an intramoiecular thioester, which undergoes intramolecular S N acyl transfer to form an amide bond.

The palladium selectively attacks an allylic acetate with inversion, even in the presence of other reactive groups, such as a C—Hal bond nucleophilic attack then occurs exclusively at the allyl group, showing the strongly activating effect of the metal (Eq. 14.80) ... 

---