Novel lithiated carbanions derived from ethyl glycosyl- and diglycosyl methylphosphonates were used in a direct and convenient synthesis of P1,P2-diglycosyl, P1,P1,P2-triglycosyl, and P1,P1,P2,P2-tetraribosyl methylenediphosphonates involving a one-pot methylidenediphosphonylation of sugars. 相似文献
Abstract A simple procedure using triangular coordinates for representing triad concentrations as a function of terpolymer compositions (and monomer proportions) is presented. Equal triad concentrations are represented by concentric closed loops or rings of equal triad concentrations converging to a unique point of highest triad concentration. The technique is illustrated with several common terpolymer systems. Alternation in terpolymer systems is assessed by determination of heterotriad concentrations. These results are compared with alternation in component binary systems. An equation is derived for calculating P12PMAX21, maximum 1,2-dyad concentration (maximum mol fraction alternation) from r1r2 product at equimolar copolymer. Alternatively, an equation is proposed for calculating P12PMAX21 from Q-e values. Uses and limitations of r1r2 product in assessing alternation in binary copolymers are discussed. 相似文献
The unexpected violet colour of P,P-tetraphenyl-oxalic acid diphosphide (3) stimulated the synthesis of the following derivatives: P,P-tetra-t-butyl-oxalic acid diphosphide (2), N,P-tetraphenyl-oxalic acid amide phosphide (4) and P, -triphenyl-glyoxylic acid phosphide (5). The compounds could be prepared by the reaction of the corresponding acyl chlorides with diorganyl-(trimethylsilyl) phosphine; (organyl=t-butyl and phenyl). The electronic transitions of green-blue2 and red5 in the 450–700 nm region are discussed, also theirv C=O in the ir spectrum. These results are interpreted in connection with the molecule structures of2 and3 which have been determined by X-ray crystal structure analysis. In2 the framework P–C(O)–C(O)–P is only slightly distorted from a coplanartrans-position, in3 somewhat more. The bonds at P have the expected pyramidal arrangement. The direction of the lone pairs at the P-atoms, derived from this bond arrangement, is discussed with respect to the electronic transitions in acyl phosphides. 相似文献
Abstract The syntheses and characterization of seven new unsymmetrical derivatives of the type YP(NMeNMe)3PZ are reported. Where Y = O or NPh: Z = S, Se, Br+ and where Y = a lone pair, Z = Br+ Also reported are the new symmetrical derivatives where Y = Z = (OC)5W or (OC)3Ni and the new monovalent cage cations YP(NMeCH2)3CMe+ where Y = Ph3C and Br. Conductivity and 31P nmr evidence for the formulation of the phosphonium cations is presented. 3J31P31P couplings, obtained directly from the 31P nmr spectra of the unsymmetrical derivatives, are found to rise upon successively oxidizing the phosphorus atoms, and a rationale is offered. This coupling is also extracted from the 183W and 77Se satellite peaks in the 31P spectra of the symmetrical derivatives where Y = Z = (OC)5W and Se, respectively. A self-consistent set of assignments of the 31P chemical shifts is arrived at for YP(NMeNMe)3PZ compounds and the useful role of LIS reagents in analyzing their proton spectra is delineated. The 13C nmr spectral parameters of these derivatives are also presented. 相似文献
P(SiMe2)3P Li3P (produced from the elements) forms with Me2SiCl2 at 20°C in toluene the bicyclic compound P(SiMe2)3P 4 beside small amounts of ClMe2Si? P(SiMe2)2P? SiMe2Cl and traces of P4(SiMe2)6 7. 4 can be transformed into 7 by thermal treatment. With the formation of 4 the existence of a bicyclic silylphosphane is confirmed which has already been mentioned in connection with P(SiEt2)3P [1], but could not be proven until now. 相似文献
Several sterically protected, low-coordinate organophosphorus compounds with P=P, P=C, and C≡P bond are described in this study. Molecules such as diphosphenes, phosphaalkenes, 1-phosphaallenes, 1,3-diphosphaallenes, 3,4-diphosphinidenecyclobutenes, and phosphaalkynes are stabilized with an extremely bulky 2,4,6-tri-t-butylphenyl (Mes*) group. The synthesis, structures, physical, and chemical properties of these molecules are discussed, together with some successful applications in catalytic organic reactions. 相似文献
A direct access to P-glycosyl-, P, P-di-glycosyl alkenylphosphonates and P, C-glycosyl phosphonates is described. The method involves the Horner reaction of an anion derived from P-monoglycosyl and P1, P′-diglycosyl methylenediphosphonates either on the exocyclic aldehyde group of carbohydrates or on the masked aldehydic form of the furanose hemiacetals. In this last case, the carbonyl olefination, followed by an intramolecular cyclization, leads to P,C-di and P,P,C-triglycosyl phosphonates. 相似文献
Abstract Experimental findings as well as quantum chemical calculations indicate that the P4 molecule has a remarkably low nucleophilicity. The P4H+ ion is predicted to have a ‘proton at apex’ configuration whereas a proton in the centre seems to be metastable. The influence of d orbitals on the stability of P4 against 2 P2 and 1/2 P8, the photoelectron spectrum, and the valence electron density is discussed. 相似文献
Abstract Reduction of PCl3 e.g. with trialkyl phosphines produces the well-known but ill-defined insoluble, amorphous, orange material approximating a phosphorus subchloride. In repeating this reduction with Ph3P and with AlCl3 as a third component we now obtained crystalline hexaphenyl triphosphenium tetrachloroaluminate. It may be thought to derive from the four electron cation P+ being complexed by two Ph3P. 相似文献
?My most exciting discovery to date has been always the last one (or better still, the next one). The biggest challenge facing scientists is the responsible use of knowledge and scientific power for the betterment of humanity. …?“ This and more about P. Melchiorre can be found on page 3389.