8-Phosphabicyclo octane derivatives

A value of 0.91 D has been calculated for the free electron-pair moment in P compounds, using dipole-moment data for P4S3 and the phosphabicyclo-octane derivative (110). Calculations for the compounds in the series PH Me3 with n - 0—3 point to variation in the free electron-pair moment as being the most important factor in determining the observed dipole moments extension to a variety of other species allows the calculation of new values for the moments of typical bonds to phosphorus. 

Regioisomeric 1,2-dihydrophosphinine 1-oxides 21A, 21B, and 24 undergo the Diels-Alder cyclization with dimethyl acetylenedicarboxylate (DMAD) to give 2-phosphabicyclo [2.2.2] octane derivatives 22A, 22B, and 25 (Schemes 7 and 8). The 1,2-dihydrophosphinine 1-oxides 26 react with phenylmaleimide to give the corresponding tricyclic heterocycles 27 (four isomers) (Scheme 9). 

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 >. 

One example performed in this laboratory is the analysis of toxicity exerted by bicyclic phosphate esters 26). 2,6,7-Trioxa-l-phosphabicyclo[2.2.2]octane-l-oxides (IS) with suitable 4-substituents (R) are highly toxic to mammals 27). The 4-Et derivative... 

Substitution of the phosphinate ester group by dimethylamine via the chloride, and thionation of the P=0 group of the 2-phosphabicyclo[2.2.2]octane P-oxide derivatives 28 with diphosphorus pentasulfide affords the corresponding amide 29 and P-sulfide 30 (Scheme 10). The thionation is also achieved with Lawesson s reagent [7,8]. Thermolysis of 28 proceeds a retro Diels-Alder reaction to give 31. 

Scheme 10 Reactions of 2-phosphabicyclo[2.2.2] octane P-oxide derivatives 28 to give 29-31...

Synthesis and Stereochemistry of 3-Phenyl-3-phosphabicyclo(3.2.1)octane and Oct-6-cne Derivatives... 

Further evidence for a biphilic insertion mechanism is derived from a study of the reaction of the bicyclic phosphoramidites (115) and (116) with diethyl peroxide to form (117) and (118), respectively. The strained 1-phosphabi-cyclo[3.3.0]octane (115) reacts much faster than its l-phosphabicyclo[4.4.0]-decane analogue (116), but the opposite reactivity is found towards diphenyl disulphide. At room temperature (116) produced (120) within seconds, presumably via an intermediate phosphonium salt, whereas (115) gave (119) [S 3ip = —19 p.p.m.] after 1 h at 58 °C. As mentioned earlier, the latter appears to be the only phosphorane reported so far with two exocyclic P-S bonds. 

Phosphole oxides also participate in a cycloaddition reaction with oxyallyl cations <75T53>, a process that gives rise to novel phosphatropolone structures. Preformed 1,2,5-triphenylphosphole oxide gave a derivative of the 8-phosphabicyclo(3.2.1]octan-6-ene-3-one ring system ((157), 91%). The oxyallyl cation (156) was prepared from a,a -dibromodibenzylketone and Nal in acetonitrile (Scheme 31). 

ReBr(CO)5 reacts with KBp to give BpRe(CO)3(Hpz). Pyrazole (Hpz) is assumed to be derived from dihydrobis(pyrazolyl)borate by a disproportionation mechanism. BpRe(CO)3(pyrazole) reacts with the phosphites P(OMe)3 and EtC(CH20)3P (4-ethyl-2,6,7-trioxa-l-phosphabicyclo[2,2,2]octane) to form the bisphosphite complexes BpRe(CO)2 P(OMe)3 2 and BpRe(C0)2(EtC(CH20)3P)2, respectively, in which the phosphites ligands are oriented trans ... 

Colourless crystals of (6.973a), 3,5,8 trioxa-1-phosphabicyclo (2,2,2)octane, mp=88-89 C, can be made by heating tris(hydroxymethyl)phosphine with trimethyl orthofonnate in the presence of a little triethylamine (6.974). The methyl derivative, P(CH20)3 CMe can be obtained using MeC (OCHPa in this reaction. 

Hassler and coworkers have studied the chemistry of oligosilylated phosphorus compounds extensively. From the reaction of MeSi(SiMe2Cl)3 with excess of Na3 / K3P they obtained the anirmic hexamethyltetrasila-l-phosphanido-3,5-di-phosphabicyclo [3.2.1]octane, which was converted to its trimethylsilylated derivative with Me3SiCl (Scheme 28) [281]. 

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