Dibromo phosphine

A similar treatment of the ethylene-phosphorus tribromide reaction has been published. When aluminium tribromide is used as catalyst, the AlBrg PBra ratio is important, and determines whether the product is the dibromo-phosphine (30) (ratio 1 320), or whether the complex (31) predominates... 

A mixture of l,4-dibromo-2,5-bis(3-sulfonatopropoxy)benzene 61 (0.78 g, 1.39 mmol), 60 (0.23 g, 1.39 mmol), Na2C03 (0.99 g) in doubly distilled water (47 mL), and DMF (20 mL) was heated at 85°C until the solids were completely dissolved. The resulting solution was cannulated to a 200-mL Schlenk flask with tris[(sulfonatophenyl)phosphine]palladium(0) (0.045 g) and the mixture was stined at 85°C for 10 h. The reaction mixture was concentrated to 25 mL by boiling and filtered. The filtrate was added dropwise to cold acetone (250 mL) to precipitate out the polymer. The polymer was collected by filtration, redissolved in a minimum of hot water, and reprecipitated by cooling. After repeating this procedure twice, the polymer was redissolved in distilled water and dialyzed for 72 h in 3500 gmol 1 cutoff membrane. After drying under vacuum, polymer 63 was obtained in 64% (0.42 g). 

Similarly, secondary phosphines and a,a -dibromo-m-xylene usually react to give diprotonated ditertiary diphosphines [44-48]. However, in the case of the fluorous secondary phosphine 12-Rfs (Scheme 2, bottom), dialkylation occurred to give the metacyclophane 13-Rfs. As detailed elsewhere [40], extensive efforts to adjust the stoichiometry to favor noncyclized products failed. Fortunately, the reduction of 13-Rfs with IiAlH4 gave some of the target ligand lO-Rfs. 

Tri-tert-butyl-X -phosphorin24 readily reacts with bromine and with chlorine. Mach oxidizing with bromine in CCI4, could not isolate a crystalline product. The brown colour of the addition product of one mole Br2 to one mole 24 disappeared with water and the crystalline 2-hydro-phosphinic acid 85b could be isolated in 45% yield. Methyl-magnesium-iodide or red phosphorus yielded 2.4.6 tri-tert-butyl-X -phosphorin 24. It seems reasonable to suppose that on bromination l.l-dibromo-2.4.6-tri-tert-butyl-X -phosphorin was formed. 

The second substitution of 1,1-dibromo-l-alkenes involved the Pd-catalyzed crosscoupling reactions of 6-8 obtained as shown in Scheme 37. Quite unexpectedly, the reaction of 6a with MeZnBr in the presence of several Pd-phosphine catalysts produced the expected cross-coupling products of >95% stereoisomeric purity in 76-91% yields, but careful ID NOE analyses have firmly established that the reaction was accompanied... 

The inherent difference in the reactivity of the 2-, and 3-positions of the pyridine ring was also exploited in an industrial application of the carbonylative coupling of pyridines. 2,5-Dibromo-3-methylpyridine was converted into the 2-monoamides using different amines with a 98 2 selectivity. Keys to the success of the coupling, which was run on the 100 kg scale, were the use of DBU as base and the replacement of the phosphine in the catalyst with 2,2 -bipyridine.84 The carbonylation of 3,5-... 

Heiss, C. Marzi, E. Schlosser, M. Buttressing effects rerouting the deprotonation and functionalization of 1,3-dichloro- and 1,3-dibromo-benzene. Eur J. Org. Chem. 2003, 4625 -629. Murahashi, S.-I. Naota, T. Tanigawa, Y. Palla-dium-phosphine-complex-catalyzed reaction of organometallic compounds and alkenyl halides (Z)-/j-[2-( N,. -di rn ethyl ami no) pheriyl]-styrene. Org. Synth. 1990, Coll. Vol. VII, 172— 176. 

Inverted names are used only for derivatives of silanes (as Silane, dibromo- and Disilane, hexachloro-), germanes, phosphine, and the like, but not for the few organic compounds. For the nomenclature of some of these and other classes of compounds, see the heading Nomenclature. 

The dithienophospholes 74 are obtained in good yields by lithiation of dibromo-bithiophenes 73, followed by addition of dihalo (aryl) phosphines (Scheme 4.22) [57]. The Lewis basicity of the P center of 74 enables a broad range of facile chemical modifications to be undertaken, as exemplified with the synthesis of derivatives 75-77 (Scheme 4.22) [57]. 

Grigg et al. also introduced another Heck-type reaction. 2,6-Dibromo-hepta-1,6-dienes 80 cyclize to the same products 83 (n = 5) as do 2-bromo-1,6-dienes 78 (n = 5) when treated with the usual precatalyst mixture, yet containing a stoichiometric amount of triphenylphosphine [63,64], In this case, palladium dibromide rather than hydridopalladium bromide is eliminated in the final step of the cross-coupling reaction, and the palladium(II) salt is reduced by the phosphine to regenerate the reactive palladium(O) species. Completely selective exo-trig cyclizations occur in these examples, however, the respective cyclohexane derivatives with n = 6 are formed in poor yields. Additionally, it is sometimes difficult to separate the product from the phosphine oxide after aqueous work-up. This latter difficulty was circum-... 

If nitrosyl bromide is allowed to react with hydrated rhodium trichloride and PPh3 in ethanol, the mixed chlorobromo complex is obtained (equation 301).13 3 When [RhCl(PPh3)3] is the substrate the dibromo complex is formed (equation 302). This complex can also be obtained from rhodium tribromide, JV-methyl-JV-nitrosotoluene-p-sulfonamide and PPh3. Replacement of PPh3 by other tertiary phosphines permits analogous dibromo complexes to be prepared (cf. equation 299). Another source of the triphenylphosphine complex is [Rh(NO)2Br] . The diiodo complex can be obtained from a similar reaction mixture containing Lil (equation 304).1293... 

Add dropwise dibromo(dibromomethyl)phosphine (120 g, 330 mmol) from the dropping funnel at a temperature between -10 and -5°C. 

One problem, as shown by the synthesis of (141), is the poor control over double oxidation of both phosphorus centers when preparing mixed phosphine-phosphine oxide ligands. One attractive solution, developed by Grushin, is a catalytic method using simple Pd(II) salts, 1,2-dibromo-ethane under biphasic conditions. In this manner (147) was prepared in high yield (>70%).308... 

Rate data for the triphenylphosphine-promoted dehalogenation of meso-l, -dibromo-l,2-diarylethanes to form ranj-stilbene in DMF are consistent with a concerted unti-elimination mechanism involving the attack of phosphine on bromine. Attack of triphenylphosphine on halogen also occurs in its reaction with the A chIoropyrroiidine-2,5-diones (82), leading eventually to the betaines (83). The... 

Recently the first use of the paracyclophane backbone for the placement of two diphenylphosphano groups to give a planar chiral C2-symmetric bisphos-phane was reported [102]. The compound 159 abbreviated as [2.2]PHANEPHOS was used as a ligand in Rh-catalyzed hydrogenations. The catalytic system is exceptionally active and works highly enantioselective [ 103]. The preparation of [2.2]PHANEPHOS starts with rac-4,12-dibromo[2.2]paracyclophane (rac-157), which was metalated, transmetalated and reacted with diphenylphosphoryl chloride to give racemic bisphosphane oxide (rac-158). Resolution with diben-zoyltartaric acid and subsequent reduction of the phosphine oxides led to the enantiomerically pure ligand 159. 

Since the double-bond isomerization was at first unrecognized and later recognized only in the hydrolysis products, the position of the double bond in most of the compounds described in the literature must be regarded as uncertain. The only proved facts seem to be that with isoprene dichloro(phenyl)-phosphine gives the 2-phospholene derivative, that dichloro(methyl)phosphine and dibromo(phenyl)phosphine give the 3-phospholene, whereas also with 2,3-dimethylbutadiene dichloro(phenyl)phosphine gives the non-isomerized product of type (1).38,39... 

Dibromo(phenyl)phosphine and (bromo)diphenylphosphine 177 White phosphorus (10 g) and... 

A rational process involving a copper catalyst in a flow tube at 360° has been worked out for the preparation of dibromo(methyl)phosphine and (bromo)dimethylphosphine and the corresponding chloro compounds ethyl halides give only poor yields by this technique, and butyl bromide does not react at all.177,178 Dichloro(trichloromethyl)phosphine has also been obtained on y-irradiation of white phosphorus in carbon tetrachloride, yields being up to 41% at 130°.179... 

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