Phosphinic as reagents

A method for the preparation of 1,3,2-diazaphospholidine heterocydes has been described by Deng and Chen (Scheme 6.225) [402], The authors found that treating hindered 1,2-diamino substrates such as a-amino acid amides with tris(diethylami-no)phosphine as reagent/solvent under open-vessel microwave conditions at 250 °C for 1 min furnished a trivalent phosphorus intermediate. Subsequent thiation of this intermediate with elemental sulfur in refluxing benzene provided the target l,3,2-diazaphospholidin-4-ones in good overall yields. The yields were much improved compared to those achieved by standard thermal methods. 

Valentine, D. H., Jr., Hillhouse, J. H. Alkyl phosphines as reagents and catalysts in organic synthesis. Synthesis 2003, 317-334. 

Alkyl phosphines as reagents and catalysts in the formation and transformation of heterocycles 03S317. 

Triptycenes 19,917 suppl. 24 Tris(diethylamino)phosphine as reagent 12,640 suppl. 23 Tris(dimethylamino)pbospliine... 

This procedure also incorporates the use of bis(3-dimethylamino-propyl)phenylphosphine as a combined amine-phosphine reagent. The merits of using this basic phosphine as opposed to a tertiary amine and a phosphine lies in the ease of workup. Excess phosphine and phosphine sulfide can be removed by extraction with aqueous dilute acid. 

Heterocyclic phosphines 32 were prepared from base-induced condensation of a secondary 1,8-diamino-naphthalene with phosphorus trichloride (the corresponding As- and Sb-analogues were obtained analogously) and converted into cyclic phosphenium cations 33 by Lewis acid promoted halide abstraction using GaCl3 or trimethylsilyl triflate as reagents (Scheme 18) [15, 92],... 

Use of tris(trimethylsilyl)phosphine as the phosphorus furnishing reagent in condensation reaction with a-diazocarboxylic chlorides (7) gave 2-trimethylsilyl-[l,2,3]diazaphospholes (9) in good yields (Scheme 3) [18],... 

Some breakthrough was finally achieved by using Pd2(dba)3 as the Pd complex, tris(tert-butyl)phosphine as the ligand, and sodium ferf-butoxide as the base [90]. This combination of reagents proved to bring about the synthesis of unsubstituted phenazine (137) by reaction of two molecules of 2-bromoaniline (131). Remarkably, no reaction takes place under the conditions of the 133 117 transformation. Currently the scope and limitations of this new sequential inter-Zintramolecular AT-arylation for the synthesis of AT-heterocycles... 

Highly enantioselective 1,5-substitution reactions of enyne acetates are also possible under carefully controlled conditions (Eq. 4.31) [46]. For example, treatment of enantiomerically pure substrate 70 with the cyano-Gilman reagent tBu2CuLi-LiCN at —90 °C provided vinylallene 71 as a 1 3 mixture of E and 2 isomers with 20% and 74% ee, respectively. This mediocre selectivity might be attributable to race-mization of the allene by the cuprate or other reactive copper species formed in the reaction mixture. The use of phosphines as additives, however, can effectively prevent such racemizations (which probably occur by one-electron transfer steps) [47]. Indeed, vinylallene 71 was obtained with an ee of 92% for the E isomer and of 93% for the 2 isomer if the substitution was performed at —80 °C in the presence of 4 eq. of nBusP. Use of this method enabled various substituted vinylallenes (which are interesting substrates for subsequent Diels-Alder reactions Sect. 4.2.2) to be prepared with >90% ee. 

Trisubstituted alkenes.9 A stereoselective synthesis of trisubstituted alkenes uses (E)-alkenyl sulfoxides (1)>U as the starting material. These are reduced to the corresponding sulfides (2)," which undergo coupling with Grignard reagents in the presence of complexes of nickel chloride and phosphines as catalyst.12 The products (3) are obtained in steroisomeric purity of > 99%. 

Organometallic complex catalysts have been removed from reaction mixtures with solid-supported phosphines as well as other ligands to facilitate reagent handling and product purification. Alternatively, Leadbeater28... 

Rntheninm complexes of alkenes, dienes, or cyclodienes in oxidation states 0 and II are known. From a preparative view, an important class of componnds is the oligomeric or polymeric complexes of composition [(dialkene)RnX2] , which often serve as reagents for further transformations. Their synthesis is similar to the procedure that has been detailed for phosphine complexes that is, when RuCl3(aq) is refluxed in alcohol in the presence of the diene, an insoluble brown to orange oligomeric complex is deposited. However, the use of... 

The clathrochelate [CoPcc(BF)]+ cation has been used as a paramagmetic phosphine shift reagent for the elucidation of the structures of transition metal complexes (in particular, (substituted-allyl)-palladium ones. Scheme 126) in solution [430, 431]. The resonance in the NMR spectra of the complexes obtained was assigned and applied to isomers and cyclic allyls identification. The reproducibility and transferability of NMR chemical shifts as well the... 

As this chapter covers two years of the literature relating to the above area, it has been necessary to be somewhat selective in the choice of publications cited. Nevertheless, it is hoped that most significant developments have been noted. As in previous reports, attempts have been made to minimise the extent of overlap with other chapters, in particular those concerned with the synthesis of nucleic acids and nucleotides to which the chemistry of tervalent phosphorus esters and amides contributes significantly, the use of known halogen-ophosphines as reagents for the synthesis of phosphines (see Chapter 1), and the reactions of dialkyl- and diaryl-phosphite esters in which the contribution of the phosphonate tautomer, (R0)2P(0)H), is the dominant aspect, which are usually covered elsewhere in these volumes. 

Zinc complexes, consisting of amine, amino alcohol, alcohol, sulfide, or phosphine as ligand, catalyzed 1,4-addition of Grignard reagents to a,) -unsaturated carbonyl compounds [447,448]. An optically active ligand on zinc achieved asymmetric 1,4-addition, the best result is presented in Eq. (204) [448]. 

Horner, L., Hoffmann, H., Wippel, H. G. Phosphorus organic compounds. XII. Phosphine oxides as reagents for the olefin formation. Chem. Ber. 1958, 91, 61-63. 

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