Acyclic carbone ligand

Scheme 16.17 Effect of an acyclic carbone ligand on selectivity in gold-catalyzed rearrangements.

Nucleophilic addition to these complexes is a little less predictable than for the dienyliron systems. For example, the nucleophiles studied add to C-3 of the acyclic dienyl ligand in (224), but to C-l of the cyclic system (225). Alkyllithiums add both to the cyclohexadienyl ligand, e.g. (227) gives (229), and to the cyclopentadienyl ligand, followed by interligand hydrogen transfer to give, e.g. (228). However, the fact that a hindered, very basic alkyllithium adds to a sterically hindered dienyl terminal carbon and does... 

For reduction of monofunctional ketones, the most effective catalysts include diamine ligands. The diamine catalysts exhibit strong selectivity for carbonyl groups over carbon-carbon double and triple bonds. These catalysts have a preference for equatorial approach in the reduction of cyclohexanones and for steric approach control in the reduction of acyclic ketones.51... 

Acyclic ligands Attached substituents are generally indicated by a prefix followed by a series of numbers representing the sequential number of carbon atoms connecting the donor atoms followed by the sequential identities of the donor atoms. 

Trost and his co-workers succeeded in the allylic alkylation of prochiral carbon-centered nucleophiles in the presence of Trost s ligand 118 and obtained the corresponding allylated compounds with an excellent enantioselec-tivity. A variety of prochiral carbon-centered nucleophiles such as / -keto esters, a-substituted ketones, and 3-aryl oxindoles are available for this asymmetric reaction (Scheme jg) Il3,ll3a-ll3g Q jjg recently, highly enantioselective allylation of acyclic ketones such as acetophenone derivatives has been reported by Hou and his co-workers, Trost and and Stoltz and Behenna - (Scheme 18-1). On the other hand, Ito and Kuwano... 

As mentioned before, acyclic substrates have been studied in detail, in particular, the reactions of 1,3-diphenylpropenyl ester (19, X=COR) or carbonate (19, X=OCC>2R), the gold standard for this class. Selected ligands for the allylic alkylation, amination, and etherification are shown in Fig. 1 and representative data are presented in Table 1. 

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