Vinylphosphines

To control the stereochemistry of 1,3-dipolar cycloaddidon reacdons, chiral auxiliaries are introduced into either the dipole-part or dipolarophile A recent monograph covers this topic extensively ° therefore, only typical examples are presented here. Alkenes employed in asymmetric 1,3-cycloaddidon can be divided into three main groups (1) chiral allyhc alcohols, f2 chiral amines, and Hi chiral vinyl sulfoxides or vinylphosphine oxides. 

A stereoselective radical reaction of the ester of M-hydroxy-2-pyridinethione (see also Sect. 4.1) to chiral vinylphosphine oxides has also been described and moderate to good diastereomeric ratios have been obtained for the compound 112 [70] (Scheme 33). 

Numerous other reactions can be used to access phosphaalkenes. For example, treating the primary phosphine Mes PH2 with CH2CI2 in the presence of KOH gives Mes P=CH2 [54]. In addition, interesting reactions of tantalum-or zirconium-phosphinidenes with aldehydes have afforded phosphaalkenes [55, 56]. The 1,3-hydrogen rearrangement of secondary vinylphosphines to phosphaalkenes has also been used to prepare phosphaalkenes [57,58]. 

Rovis and co-workers have also shown that pre-catalyst 129 is competent with a wide range of Michael acceptors including oc,P-unsaturated aldehydes, amides, nitriles, esters, thioesters, vinylphosphonates and vinylphosphine oxides (Scheme 12.25) [58,60],... 

Similar additions also occurred on vinylphosphine oxides. When the optically active vinylphosphine oxide was used, P-chiral alkylphosphine oxide was obtained with retention of the configuration (Eq. 10.27)60... 

Recent work in the chemistry of phosphorus heterocycles derived from a-hydroxyalkylphosphines and vinylphosphines, much of which has appeared in the Russian language literature, is covered by B. A. Arbuzov and G. N. Nikonov (Kazan, Russia). 

Several reports have been made of the application of this procedure for the preparation of vinylphosphonates129-131 as well as tertiary vinylphosphine oxides132 in good yield. When formaldehyde is used, this approach provides a convenient method for the preparation of chloromethylphosphonic dichloride.133 Extreme caution needs to be exercised in the performance of this reaction because the extremely hazardous bis-chloromethyl ether is generated as an intermediate and may remain in the product or escape the reaction mixture during performance of the reaction. 

By Addition ofP—H to Unsaturated Compounds. This route continues to be exploited for the synthesis of polydentate tertiary phosphine ligands. Thus base-catalysed addition of diphenylvinylphosphine to the secondary phosphine (25) affords (26).23 Neopentylpolytertiaryphosphines, e.g. (27), have been similarly prepared24 by addition of primary or secondary phosphines to vinylphosphines (or the related phosphine sulphides, followed by a desulphurization step). 

Various -substituted vinylphosphine oxides (14) have been made by the Wittig route, and found to be /raws-isomers.17 The geometry of these oxides is believed to be... 

Shift reagents have been used for the configurational and conformational analysis of cyclic phosphites (34).65 The reagent Eu(fod)3 moved Ha of the vinylphosphine oxide (35) twice as far downfield as the corresponding proton in the spectrum of the... 

In ethanol/water mixtures addition of sodium mercaptoalkane sulfonates on vinyldiphenylphosphine proceeds smoothly at room temperature and yields a variety of tertiary phosphines such as 24. Interestingly, at the beginning of the reaction the ethanolic solution of the vinylphosphine and the aqueous solution of the educt comprise two separate phases and this is favourable for the high yields obtained (59-97%) [30]. 

The ligand 2-allylpyridine is reported to form chelate complexes with copper(I) chloride, silver nitrate and platinum(II) chloride (29). Diphenyl vinylphosphine also forms stable 1 1 and 2 1 adducts with silver nitrate in which both the phosphorous and the double bond are thought to be coordinated to silver (30). 

Brandi and co-workers (29,30) smdied the 1,3-dipolar cycloadditions of chiral a,p-dialkoxynitrones with vinylphosphine oxides (Scheme 12.8). The reaction of optically active 15 with vinylphosphine oxide 16a gave a 65 14 mixture of the... 

The first example in Scheme 10.1 shows that vinylphosphine kinetically first gives the three-membered heterocycle (75%), which upon heating transforms into the thermodynamic product, the four-membered heterocyclic complex. From the other examples we see that, ifthe possibility exists, the preferred route is formation ofa fivemembered ring [18]. 

Synthesen von Heterocyclen mit Hilfe von Alkylidenphosphoranen, Phosphinimiden, Vinylphosphonium-salzen und Vinylphosphin-oxiden E. Zbiral, Synthesis, 1974,775-797. 

The 1 1 addition of RPH2 to a vinylphosphonate (Equation 4a) proceeds effectively under base-catalyzed conditions in contrast to the 1 1 addition of RPH2 to a vinylphosphine (Equation 3). This point can be related to the basicity of the anions involved as intermediates in the Michael-type addition of phosphorus-hydrogen compounds to vinyl-phosphorus derivatives (12). 

Vinylphosphines. A general route to vinylphosphines involves deprotonation of trisylhydrazones of ketones with u-hulyllithium (or vec-butyllithium) followed by... 

Pentacarbonyl(trimethylsilyl)manganese. VINYL FLUORIDES Pyridinium poly(hydrogen fluorideV-N-Bromosuccinimide. VINYLPHOSPHINES 2,4,6-Trii sopropy I benzenesulfonylhy drazine. VINYL SELENIDES Benzeneselenenyl halide-Silver nitrite. Diphosphorus tetraiodide. 

Arbuzov, B. A., Nikonov, G. N., Phosphorus Heterocycles from a-Hydroxy alkylphosphines and Vinylphosphines, 61, 59. 

Warren and coworkers have reported an interesting synthesis of nonracemic allenes by reaction of vinylphosphine oxides with aldehydes in the presence of chiral lithium [(R)-l-phenylethyl](benzyl)amide to give hydroxyvinylphosphine oxides in 33-87% yields (0-51% ee) [38]. These products underwent a Horner-Wittig elimination reaction to produce nonracemic allenes. A mechanism similar to the Baylis-Hillman reaction was suggested. 

The complete hydrogenation of vinylphosphine oxide 148 and 149 was achieved in one step by hydrogenation with palladium on carbon catalyst using 5 equiv of hydrogen <2000SC4221> (Equation 33). 

The preparation of P-O containing heterocycles from bis(diisopropylamino)vinylphosphine (71) was reported by van Boom and co-workers <00TL8635> (Figure 8). 

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