Allylation phosphoramides

The presence of propionic acid in small quantity beside the a-hydroxy phosphonamide 5 when 0-allylic phosphoramide 4 is treated lay one equivalent of n-Butyllithium has required the analysis of the conditions of its formation ( 2). ... 

Diethyl N-allylic phosphoramidates (95) isomerize to diethyl 1-alkenylphosphoramidates when irradiated (uv) in the presence of Fe(CO) the (E)-form of the product (96) is favoured and the yields are better than those obtained during alkylation reactions of (97) to form (98) as indicated. 

Allylic trichlorosilanes have shown promise in the development of methods for enantioselective reactions by use of chiral phosphoramides such as C. 

A series of N-allyl sulfamates, phosphoramides, and phosphorimidates was prepared to explore the possibility of O- N rearrangements via the intermediacy of the contact alkene radical cation/anion pair, followed by 5-exo-trigonal radical cyclizations (Fig. 4) [142],... 

RBr, phosphoramidate or polyamine (on KOAc R— 1° alkyl, allyl, benzyl, o-keto)... 

S)-Prolinc-dcrivcd phosphoramides catalyse enantioselective allylation of aromatic aldehydes with allylic trichlorosilanes.90 Chiral a-aminoaldehydes have been allylated diastereoselectively with various reagents.91... 

Stereo specific generation and reactions of allylic alkali and alkaline earth metals have been reviewed121 and solvent-mediated allylation of carbonyl compounds with allylstannanes has been explored.122 Chiral phosphoramides derived from (5 )-proliiie have been used to catalyse asymmetric allylation of aromatic aldehydes by allylic trichlorosilanes.123... 

Chiral phosphoramides have been developed as catalysts for asymmetric addition of allylic trichlorosilanes to aldehydes.176 Although some des were high, ees were modest. Kinetic studies suggest dual mechanisms, and thus a route to the design of more highly selective catalysts. 

The phosphoramide-catalyzed allylation of aldehydes is probably the most intensively investigated organocatalytic allylation reaction to date [164], The first exam-... 

In addition to phosphoramide-based organocatalysts, chiral C2-symmetric formamides were found to be versatile catalysts the asymmetric allylation of aide-... 

For a recent summary of the Lewis-base-catalyzed allylation with a main focus on phosphoramide catalysts, see S. E. Denmark, J. Fu, Chem. 

Chiral Lewis-basic catalysts (Figs. 7.1 and 7.2), in particular phosphoramides 8-12 [9, 14c, 15c, 22-24], formamide 13 [17], pyridine N,N -bisoxides 17 and 18 [25-27], N-monoxides (19-26) [27-32], and N,N N"-trisoxides (27) [33] exhibit good to high enantioselectivities for the allylation of aromatic, heteroaromatic, and cinnamyl-type aldehydes (1) with allyl, trans- and ds-crotyl, and prenyl trichlorosilanes (2a-d). Chiral formamides (with the exception of 13, as discussed below) [17], pyridine-oxazolines [34], urea derivatives [19] and sulfoxides [35] are effective only in stoichiometric quantities (or in excess) and, as a rule, exhibit lower enantioselectivities. 

The early phosphoramides 8 and 9 (Fig. 7.1), developed by Denmark [22], exhibited modest enantioselectivity in the allylation reaction (Scheme 7.1 and Table 7.1), but played an important role in the mechanistic elucidation and development of the second generation of catalysts (vide infra). The proline-derived phosphoramide 10 proved more selective (Table 7.1, entry 2) [14c, 15c], but its preparation is hampered by the fact that, unlike with 8 and 9, its phosphorus atom is stereogenic, so that two diastereoisomers are formed and need to be separated. Phosphoramide 10 has been reported to give higher asymmetric induction than its diastereoisomer (entry 2) [22f ]. However, the results are further affected by the variation of the N-substituents generally, the sense of asymmetric indue-... 

Chiral phosphoramidates attached to polystyrene have also been reported to exhibit asymmetric induction in the allylation of PhCHO with AllylSiCl3 (< 63% ee) Oyama, T., Yoshioka, H., Tomoi, M., Chem. Commun. 2005, 1857. 

In the palladium-catalyzed allylic amination reaction, primary and secondary amines can be used as nucleophiles, whereas ammonia does not react. Therefore, many ammonia synthons have been developed, and a variety of protected primary allyl amines can now be prepared using azide, sulphonamide, phthalimide, di-f-butyl iminocarbonate ((Boc)2NLi), and dialkyl A-(rerr-butoxycarbonyl)phosphoramide anions as the nucleophile [20], An example of the use of ((Boc)2NLi) 30 as the amine nucleophile in the palladium-catalyzed allylic amination reaction is shown in Eq. (9). This reaction also illustrates the problem with the regioselectivity in the reaction as a mixture of the products 31-33 are obtained [21]. 

Introduction. [45-(4a,5p)]-1 -(1,3-Dimethyl-2-oxido-4,5-di-phenyl-l,3,2-diazaphospholidine-2-yl)piperidine (la) and its derivatives are an important class of phosphoramides which have seen much success as Lewis-basic catalysts for aldol additions, allylations, crotylations, and epoxide openings. The three nitrogen subunits of the phosphoramide provide the opportunity for a large number of structurally diverse analogs, allowing a wide spectrum of properties and shapes to be customized. ... 

The phosphoramide-catalyzed allylic additions to aldehydes have also been extended to include stereoselective crotylations. When using geometrically defined 2-butenyltrichlorosilanes, additions to benzaldehyde afford homoallylic alcohols in good yields and excellent diastereoselectivity (eq 11). Enantioselectivities, however, remain comparable to the results for allylic additions. Interestingly, the crotylation results suggest that addition proceeds through a cyclic transition structure. ... 

Dimeric phosphoramides have recently been demonstrated to be superior to the monomeric versions for allylations and crotylations using allylic trichlorosilanes, see reference 21b. 

Notable were highly enantioselective additions of N-phosphonyl imines with dialkyl zinc or hydroxyketones and a one-pot reaction of alkynylzirconocenes with alkynyl phosphazenes and zinc carbenoids to give single isomer cyclopropylphosphonamides. The importance of enantioselective and dynamic kinetic asymmetric transformations is illustrated in many publications. Other interesting reports cover the use of phosphoramidates for the synthesis of allylic amines as well as the first example of C-P cleavage of a-aminophosphono acids using periodate. 

In contrast to the anion of diethyl phosphoramidate or trifluoromethanesulfonamide, which cannot be cleanly monoalkylated, - the anion of trifluoroacetamide (100) was monoalkylated by alkyl halides or alkyl methanesulfonate. The resulting A -alkylamides (101) were converted into primary amines by alkaline hydrolysis or reduction (NuBHa Scheme 42). Various primary amines were prepared from (100) with primary alkyl iodides or methanesulfonate, benzyl and allyl halides, a-bromocarbonyl compounds and 2,4-dinitrochlorobenzene. However, competitive elimination is a serious side reaction for less reactive primary alkyl chlorides and secondary halides or methanesulfonate. The synthesis of secondary amines from (100) has also been reported. ... 

The syntheses of the 5 -phosphoramidates and 5 -diphosphates of 2 -0-allyl-P-D-arabinofuranosyl-uracyl, -cytosine and adenine (96) have been described. 

In their initial disclosure on the chiral phosphoramide-catalyzed allylation of aldehydes with allyltrichlorosilanes, Denmark also reported that allyltrichlorostan-nanes were effective, albeit in significantly lower yield and selectivity (cf. Scheme 10-31 51% yield, 16% ee) [55]. 

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