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This paper describes the photochemical and the thermal isomerization of s-cis (E,E) 1,1-diphenly-3,4-bis(trimethylsilylmethylene)-1-silacyclopentane ( 1a ). Under thermal conditions a 1,3-sigmatropic of the methylene hydrogen occurs, yielding the s-trans isomer ( 1b ). The photochemical irradiation of ( 1a ) at 300 nm for 1 h in deoxygenated benzene gives the corresponding s-cis ( E , Z ) isomer ( 1c ) and then the s-cis ( Z , Z ) isomer ( 1d ) after prolonged irradiation (3 h). There was no evidence for the formation of the corresponding cyclobutene resulting from the ring closure of the exocylic diene.

The diallylic phosphine-borane Ph(BH3)P(allyl)26, reacts with the zirconocene ‘Cp2Zr’ and gives the bicyclocomplex intermediate 7, characterized by 1H and 31P NMR. The electrophilic addition of H+, Br2, PhPCl2(BH3), Ph2PCl(BH3) leads to the corresponding stabilized phospholanes 8, 9, 11 and bicyclophospholane 10, whereas Ph2P(BH3)Li on 9 gives the boro(phospholane–diphosphine) 12. Under the same conditions, the tetraallylsilane (or germane) 13a–b leads to the spirometallacyclopentane 14a–b intermediates. After reaction with Br2, Ph2PLi(BH3) and PhPCl2(BH3), the racemic spirannic tetraphosphines 16a–b and the protected spirannic diphosphine 17b are obtained with a remarkable selectivity. Decomplexation reaction by Et2NH gives corresponding free phosphines 3′–17′.

The dipropargylic derivatives of Si, Ge, P, 1a–c, react with the zirconocene entity ‘Cp2Zr’ and give the intermediate bicyclocomplexes 2a–c characterized by 1H and 31P-NMR. The electrophilic addition of H+, Br2 leads to the corresponding exo dienic metallacyclopentanes 3,4. The cyclozirconation reaction with hetero-diallylic compounds 5a–d gives the metallacyclopentanes 7–15, after reaction with different electrophiles such as H+, PCl3, PhPCl2, Ph2PCl or Ph2PCl(BH3), Br2. The cyclozirconation reaction of diynes is stereoselective and leads to the E,E-exocyclic dienes whereas the selectivity of cyclozirconation of dienes depends on the substituents on the heteroatom.

The synthesis of ortho-substituted benzoic acid 3 from benzalphthalide 1 in the presence of ‘hydriodic acid—red phosphorus’ (HIaq/Pred) occurs via the formation of benzylphthalide 2 as reaction intermediate. Its preparation is optimized by use of the ‘supported reaction in dry media’ process (Silica/HIaq) under microwave irradiation for 8 min. The role of the red phosphorus in the reduction reaction is elucidated: it intervenes in a catalytic cycle by an oxido—reductive disproportionation with the liberated iodine, affording either hypophosphorous acid in aqueous media, or P2I4 in anhydrous media with concomitant regeneration of HI. Thus, the presence of Pred in the couple ‘HIaq/Pred’ allows recycling of the hydriodic acid and enhances its reducing efficiency.

The unsymmetrical diphosphirane 2a , obtained by addition of dichlorocarbene to the corresponding diphosphene ArPPTsi (Ar  2,4,6,-tri-tert-butylphenyl; Tsi  tris(trimethylsilyl)methyl) presents a structure with the shortest PP bond (2.117 A) ever observed in the diphosphirane series, and a torsion angle (Ar)CPPC(Tsi) close to 180° (177.0°). A shortening of intra- and extracyclic PC bonds, as well as of CCl bonds, is also observed comparative to the symmetrical diphosphirane 1a . Such short bonds can account for the special chemical behaviour of 2a . The anionic ring opening of the diphospharine 1c leads to the stable 1,3-diphosphaallyl anion 7c . The equivalence of the two phosphorus atoms and the existence of a PLi coupling constant of 41 Hz is an argument for a σ-allytic structure in solution.

The bis-allylic 1 and the bis-propargylic 6 derivatives react with the zirconocene “ZrCp2” and lead, after electrophilic addition, to the corresponding chiral trans heterocyclopentanes (MSi,Ge,P) 3–5 and bis-methylenecyclopentanes 8. New chiral diphosphine 9 is obtained starting from the intermediate complex 2 or the functionalized heterocyclopentane 4.

Ultrasound irradiation enhances the rate and improves the yield of the heterogeneous asymmetric Michael reaction without any modification of the enantioselectivity with respect to standard procedure. These improvements are assigned to ultrasonic mechanical effects.

The generation of phosphine PH 3 by alkaline hydrolysis of red phosphorus is realized. The subsequent alkylation of PH 3 by terminal alkenes and alkynes in basic media leading to the corresponding aliphatic and vinylic phosphine derivatives can occur by two-steps or one-pot reaction by a Michael-like reaction mechanism.

The metallation reactions of the functionalized diphosphiranes 1a,b with the anionic metal transition complexes Na[(Cp)nM(CO)m] (M  Mo, W, or Co) afford σ- or π -diphosphaallyl complexes depending on the substituents of the intracyclic carbon atom. The same complexes are also obtained from their photochemical isomers, the 1,3-diphosphapropenes 2a,b. The complexes are thermally labile as shown by variable-temperature NMR spectroscopy. Upon heating, the σ-diphosphaallyl cobalt complex 3aC is irreversibly transformed into the π-complex 4aC. In contrast, with M  Fe and in toluene solution at reflux, reduced 1,3-diphosphapropenes 5a,b are obtained. Further, the gem-dihalogenated diphosphiranes 1c,d and their isomers 2c,d lead quantitatively to 1,3-diphosphaallene 6 under the same metallation conditions. The mechanism of the coordination reactions is discussed.

The reaction of saturated and unsaturated organomagnesium compounds with the monohalogenated diphosphiranes, 1a - b , and their isomers, the 1,3-diphosphapropenes, 2a - b , leads to a series of substituted 1,3-diphosphapropenes and 1,3-diphosphadienes 4 - 8 ( a - b ), but with the dihalogeno-derivatives 1c - d and 2c - d , it gives quantitative yields of 1,3-diphospha-allene 9 . The reaction occurs via an anionic ring-opening involving an allylic anion intermediate 11a - b , detected by 31 P NMR.

Sonication improves substantially the rate of formation of diphosphene 1 with respect to standard procedures. The cyclopropanation of 1 using sonochemical generation of methylene or halogeno-carbenes constitutes an interesting alternative in the diphosphirane synthesis. Furthermore, ultrasonic effects in a chlorinated solvent allow the first substitution of a diphosphirane without ring-opening.

In the diphosphirane serie, whereas the fragmentation is a side reaction during the photochemical, thermal or cationic ring opening, the oxidation of the phosphorus lone pairs leads quantitatively to the corresponding phosphaalkenes, and the unstable phosphinidene.

The synthesis, with asymmetric induction, of chiral hexacovalent phosphorus anions, allows a polarimetric kinetic study of epimerization or racemization mechanism of these compounds which is shown to be irregular (acid catalyzed).

Resume Une vingtaine de spirophosphoranes nouveaux (Tableaux 1 et 2) ont ete prepares en faisant reagir les &alpha-aminoacides sur des composes du phosphore tricoordine possedant un groupement partant convenable. Dans le cas du compose 1i , un equilibre chaǐne-cycle P III P v a ete mis en evidence.

Diphosphiranes 3a - 3f are obtained by action of diazo derivatives and carbenes on the trans-diphosphene 1 . The structures are elucidated by spectroscopic methods. In all cases the cycloaddition reaction is stereoselective.

We have prepared phosphite ozonides 1b – 3b which are efficient and clean singlet oxygene generators at low temperature.

Resume A compound has been isolated whose elemental analysis, nmr and IR data are consistent with an equilibrium phosphoranide phosphite.

Spirophosphoranes with a P-OH bond have been prepared as free acid (compound 5c), triethylammonium salts (compounds 2c–6c), or adducts 1 1 with DMF (compounds 5c and 6c). The ionic feature of triethylammonium salts of compounds 1c–6c, shows that these Spirophosphoranes are relatively strong Bronsted's acids. Tautomeric equilibrium phosphoric ester—phosphorane with a P-OH bond [Scheme 9), shown in many cases, has been studied by means of 31PN, MRspectroscopy. Influence of factors ruling this equilibrium is analysed. Some elements of dynamic stereochemistry are examined.

We have obtained phosphorus ozonides ( 3b , 4b and 5b ) in which phosphorus atom is hexacoordinated. In solution, these adducts are more stable than pentacovalent phosphorus homologs (ΔC* = 23 kcal.mole−1 for 4b )

The functionalized diphosphiranes 1 a–c, in presence of Lewis acid, undergo two kinds of reaction:the ring opening leading to the phosphenium-phosphonium ion 2a–c obtained according to an electrocyclic reaction and the fragmentation giving phosphaalkene 3a–c and phosphonium ion 4. The deprotonation reaction of 2a–c in hexane leads to phosphino-phosphaalkenes 6a–c.

The 3,3-dihalogeno-1,2-diphosphiranes 1(a–b) and its photochemical isomers, the 2,3-dihalogeno-diphosphapropenes 8(a–b) lead to the 1,3-diphosphaallene 4 by action the methyllithium. The anionic ring opening mechanism appears most likely.