Phosphines nonracemic

Many attempts have been made to develop novel nonracemic ferrocenyl phosphine derivatives as asymmetric hydrogenation catalysts. Interested readers will find the design and synthesis of these chiral ferrocenyl phosphine ligands in a recent review by Richards and Locke.286... 

Diols are directly converted into oxiranes with Ph3P or other phosphines in the presence of diisopropyl azodicarboxylate (Mitsunobu reaction). Simple alkenes can be converted into nonracemic epoxides in high yields and with excellent ee values via a two-step sequence of asymmetric dihydroxylation and Mitsunobu cyclodehydration of the intermediate diol (Scheme 18) <20010L2513>. These reactions give best results using electron-poor alkenes . 

Xu et al. have further expanded the scope of Pd-catalyzed CsfP—P bond formation reactions to include a variety of different organophosphorous coupling partners [83]. For example, the coupling of 2-bromothiophene with n-butyl phenyl phosphite was effected to form //-butyl diarylphosphinate 82. This chemistry also allows for the synthesis of alkyl arylphenylphosphine oxides, functionalized alkyl arylphenylphosphinates, alkenyl arylphenylphosphinates, alkenylbenzyl-phosphine oxides, as well as chiral, nonracemic isopropyl arylmethylphosphinates [84]. Intramolecular Pd-catalyzed CspR— P bond formation has also been reported [84]. 

Asymmetric Allylation Reactions. Enantioselective allylic alkylation is used extensively in asymmetric synthesis with chiral nonracemic phosphines often serving as the source of enantio-discrimination. A monodentate phosphabicyclononane derivative in conjunction with Pd(dba)2 was found to be effective in promoting the asymmetric allylation of 2-substituted cyclopen-tenyl and cyclohexenyl carbonates with malonate and sulfonamide nucleophiles with ee s ranging from 50 to 95% (eq 16). ... 

Using 4 mol % of Pd(dba)2 plus 4 mol % of a chiral phosphine ligand such as BINAP, DIOP, MOD-DIOP, and ferrocenyl phosphines, the reaction of Phi, ( )-l-phenyI-I,2-butadiene, and sodium dimethyl malonate afforded chiral nonracemic (5)-dimethyl 1-methyl-2,3-diphenylallyl malonate 69 with up to 96% ee (Scheme 26)3" ... 

Important applications of a-amino boronate esters have been found in pharmacology [103]. Recently, Fernandez and co-workers [104] developed an enantioselective pinacolboryl addition to tosyl aldimines in the presence of chiral nonracemic phosphines to form enantiomerically enriched a-amino boronate esters. Fine-tuning of the reaction conditions in terms of base and additives was first necessary to promote the nucleophilic addition of bis(pinacolato)diboron methoxide anion adduct to the imine. A screening of chiral mono- and diphosphines was then undertaken, showing compound 36 as the best organocatalyst to afford products in good yield and... 

Asymmetric Mannich-type reaction is a versatile method to prepare nonracemic P-amino carbonyl compounds, which can be transformed into P-lactams or related compounds. Lectka and coworkers have shown that a BINAP-silver(I) complex acts as asymmetric catalyst in the reaction of a-imino esters for the first time in 1998 [58]. The chiral silver (I) catalyst has been further applied to asymmetric ene reactions of a-imino esters [59, 60]. In contrast, Hoveyda and co workers have developed a new chiral silver(I) catalyst using iso-Leu-derived phosphine (44) as a chiral ligand, which promotes asymmetric Mannich reaction of silyl... 

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