Phosphane production

The bis(imino-A5-phosphane) 4 (0.508 g, 0.7 mmol) in CH2C12 (25 mL) was slowly treated with an aroyl chloride (0.7 mmol) and Et3N (0.07 g, 0.7 mmol) and the mixture was stirred at 20 C for 7 h. The solvent was removed in vacuo, benzene (15mL) was added, the precipitated Et3N HC1 was filtered off and the filtrate was evaporated under reduced pressure. Chromatography of the residue (silica gel, EtOAc/hexane 1 2) gave the red product, which was recrystallized (EtOH). 

The parent compound, 69, has been synthesized and characterised <2003ZFA1475>. 4-Chloro-hepta-l,6-diene was reacted with Mg. No Grignard rearrangement was noticed but instead the Grignard reagent was converted into l-allyl-3-butenylphosphonous dichloride by reaction with PC13. Reduction with LiAlH. produced l-allyl-3-butenyl-phosphane. Radical-initiated cyclization led to the product, l-phosphabicyclo[3.3.0]octane. Four derivatives were similarly prepared and characterized (70-73). Compound 74 was similarly prepared via a radical reaction < 1997PS(123)141 >. 

Whereas the reactions of allenephosphonates 171 (R2 = OEt) with primary aliphatic and aromatic amines 172 and the reactions of the phosphane oxides 171 (R2 = Ph) with aliphatic amines 172 afford the conjugated addition products 173 always in good yields, the addition of anilines to 171 (R2 = Ph) leads to an equilibrium of the products 173 and 174 [231]. However, treatment of both phosphane oxides and phos-phonates of type 171 with hydroxylamines 172 (R3 = OR4) yields only the oximes 174 [232, 233]. The analogous reaction of the allenes 171 with diphenylphosphinoylhy-drazine furnishes hydrazones of type 174 [R3 = NHP(0)Ph2] [234],... 

The ring closure to form butenolides by palladium(O) catalysis can be combined with C,C bond linking, as shown by Ma and co-workers. If using tetrakis (triphenyl -phosphane)palladium(O), the products 272 are obtained from 268 (R1 = alkyl, R2 = H) and vinyl iodides or aryl bromides and iodides R3X [304]. The authors assume that... 

Allenic esters such as 185 can act not only as dipolarophiles but also, at least formally, as 1,3-dipoles, which was shown by Xu and Lu during the phosphane-cata-lyzed reaction with N-tosylimines 387 (Scheme 7.52) [358, 359]. The heterocycles 388 are formed at least in moderate and mostly in excellent yields, if R1 is an aryl or a vinyl group. The formation of the products can be explained by reversible nucleophilic addition of the phosphane to 185 (cf. Section 7.3.1) followed by nucleophilic addition of the resulting intermediate to the imine 387. 

The main products under all variations of R and R are the P2-chlorinated triphosphanes. Side reactions such as SiMe3/Cl exchange, P—P cleavage by LiP(SiMe3)R, or transmetallations take place only to a small extent. MeP(SiMe3)2 is an exception inasmuch as it reacts with P-chlorinated phosphanes to yield tri- and even tetraphosphanes. 

Alkylidene-phosphapyrazolines 98-101 are much more thermally stable than their relatives 88, which do not possess the exo-methylene substitution. Dediazo-niation of 98 required heating in toluene at 110°C and gave one or more of the following products, probably via intermediate diphenylmethylene(vinylidene)phos-phoranes methylenephosphiranes, (2-siloxyvinyl)phosphanes, 2//-l,3-oxaphos-pholes, and l-alkylidene-2,3-dihydro-l//-benzo[c]phospholes (169). Thermolysis of 100 ( R = t-Bu, 1-adamantyl) afforded isolable 2-phosphabutadienes (169). The photochemical elimination of N2 from 98 generated cyclic azomethine imine dipoles 104 (Scheme 8.24), which rearrange to compounds 105 and 106 that could be further trapped with DMAD to form 107 (170). 

Little is known about using a P=S bond as a dipolarophilic unit. Indirect evidence of a 1,3-dipolar cycloaddition in the case of 2,2-dimethyl-1-diazopropane with the short-lived amino(thioxo)phosphane R2N—P=S (R = SrMc3) exists (190). More remarkable is the formation of 1,3,4,2-thiadiazaphosphohne 182 from diazo compound 180 and 0.5 equiv of Lawesson s reagent (179) (Scheme 8.41) (241). This and similar results with nitrones and nitrilimines suggest that the monomeric dithiometaphosphate form of 179 can be trapped in a dipolar cycloaddition across the P=S bond. A spontaneous 1,3-R shift in cycloadduct 181 would then lead to the final product. 

The chemical shift differences of the diastereotopic hydrogens are listed in Table 17 they depend strongly on solvent effects, as expected for an ionic product. They are in the range of 8 = 0.01 -0.1, well suited for measurement of the enantiomeric purity of the phosphanes. An alternative method for the measurement of Horner phosphanes is by 13C-NMR spectroscopy of diastereomeric complexes formed with [>/3-( + )-0 7 ,57 )-pinenyl]nickel bromide dimer73. 

The electrochemical allylation of carbonyl compounds by electroreductivc regeneration of a diallyltin reagent from allyl bromide and a Sn species leads to formation of homoallylic alcohols in yields of 70-90 % even in methanol or methanol/water (Table 7, No. 12) Bisaryl formation is possible also from aryl iodides or bromides in the presence of electro-generated Pd phosphane complexes (Table 7, No. 13) In the presence of styrenes, 1,3-butadienes, or phenyl acetylene the products of ArH addition are formed in this way (Table 7, No. 14) . The electroreductivc cleavage of allylic acetates is also possible by catalysis of an Pd°-complex (Table K No. 15)... 

The electrochemical oxidation of tertiary phosphanes, R3P, can be carried out with a platinum electrode in acetonitrile with the addition of pentylammonium fluoride and with the electrolyte tetraethyl ammonium tetrafluoroborate.65 The observed product is the trialkyldi-fluoro-25-phosphane R3PF2. The electrolysis is carried out in a galvanostatic mode with a current density from 3.3 to 6.7 mA cm-2. The anodic oxidation may be represented by the following equation ... 

Similarly, the reaction between sulfur tetrafluoride and tris(dimethylamino)phosphane proceeds with oxidation of the phosphane in addition to fluorine transfer to give tris(dimethylamino)-difluoro-A5-phosphane (18) as the main product. In contrast, the reaction with tris(methyl-sulfanyl)phosphane does not give a straightforward fluorination extensive Arbuzov-type rearrangements and fluorination reactions occur.220... 

Tangible evidence was found for the in situ production of perfluoro(2,3,4,5-tetrahydro-pyridines) 2, 3, and 4 during the transfer of F- from perfluoro-l-fluoropiperidine (1) to carbanionic sources.22 23 Perfluoro-l-fluoropiperidine (1) was employed to convert triphenyl-phosphane, -arsane, and -stilbane to the difluorides, triphenylphosphorus difluoride, triphenyl-arsenic difluoride, and triphenylantimony difluoride, respectively,24 and sodium phenoxide to 2- and 4-fluorophenol.25 Perfluoro-l-fluoropiperidine (1) reacts with 7V,/V-dimethylaniline, substituting the 0/7/m-hydrogen by fluorine. A similar reaction proceeds with /V,/V-diethylaniline.26... 

The second product in this reaction, the difluorotris(perfluoroalkyl)-A5-phosphane, does not dissolve in aryl fluorides and, because of its greater density, forms a lower layer which can be easily separated. In this way the difluoro-A5-phosphanes are regenerated almost quantitatively and can be used in the synthesis many times. An example is the decomposition of 4-nitrobenzene-diazonium trifluorotris(heptafluoropropyl)phosphate at 87 C which provides l-fluoro-4-ni-trobenzene in 82% yield and difluorotris(heptafluoropropyl)-A5-phosphane in quantitative yield.6 This method is a convenient modification of the Balz-Schiemann reaction (see Section 26.1.3.). 

---