Bicyclic phosphoranes

The spirophosphorane (74) has been identified as an intermediate in the formation of (75) from o-aminophenol and trisdiethylaminophosphine.61 With ethylene glycol (75) gave high yields of the phosphoranes (76) and (77). As expected, the phosphoranes (78) have apical fluorine atoms.52 The interesting bicyclic phosphoranes (79) and (80) have been prepared as shown.63... 

Monocyclic phosphoranes and fused bicyclic phosphoranes with a... 

Addition of trifluoromethanesulfonic (triflic) acid to a CDCI3 solution of (,yj) gives alkoxyhydridophosphonium salt (fy). Hellwinkel s (7) bicyclic phosphorane Q behaves in an analogous manner. An increase of about 300 Hz in the value of IjpH upon formation of from is consistent with a smaller... 

Conversion of Bicyclic Phosphoranes into Phosphoranides and Phosphane Adducts with Transition Metal Derivatives... 

Bicyclic phosphoranes of type (7) are structurally adapted to be in tautomeric equilibrium with open forms such as (8), in which the phosphorus atom is in valence state 3. The nitrogen atom is planar in (7) but becomes pyramidal in (8) and would be expected to recover its donor properties. Tautomer (8) has never been detected spectroscopically (72TL2969). Through the action of various atoms or cations, the bicyclic phosphoranes can be converted into coordination adducts of tautomer (8). The bidentate character of (8) has been demonstrated by X-ray diffraction of the complex (9) obtained from (7) and Rh(CO)2Cl2 in toluene (79JA2234). 

Similar bicyclic phosphoranes 51 are formed in the reactions of phosphorus isocyanates and isothiocyanates with HFA (97,176,239) via intermediate formation of oxazaphospholinones and -thiones 50. 

Reaction at the P-substituent of a phosphole has been proposed to rationalize how 2-acylphospholide anions 147 react with dihalogenomethanes in the presence of a strong base to give the / -functionalized phosphinines 148 (Scheme 43) <2005AGE1082>. The proposed mechanism, supported by DFT calculations, involves the formation of intermediate phospholes 149 that evolve to yield the bicyclic phosphoranes 150 via an intramolecular Sn2 reaction. 

Devillers et al. have also implemented a 1,3 van der Waals term in MM2, but the goal was to treat conformations of bicyclic phosphoranes.i -i The conformational energies of various molecules were calculated and compared to NMR data. The molecular mechanics energies matched (with some exceptions) the NMR data for the molecules. 

G. Robinet, M. Barthelat, J. Devillers, V. Gasmi, D. Houalla, and R. Wolf, Struct. Chem., 2, 11 (1991). Molecular Mechanics Extension of the MM2 Program to Pentacoordinate Phosphorus Compounds. 1. Conformational Study of the Bicyclic Phosphoranes of the Type R-PiHlNfCHjCH O) (R = H, Me, Ph). 

Further contributions to the study of the interaction of trico-ordinated phosphorus compounds with carbonyl compounds have been reported by Pudovic et al. In the first of these,a phosphoroisocyanitidite (83) reacts with the two moles of hexafluoroacetone (46) in ether at -25° to form the bicyclic phosphorane (85) via the ylid intermediate (84). Similar reactions occur with alkyltrifluoropyruvates ( CF3CO.CO2R, Me or Et) as substrates. In the second paper, the reaction of dimethyl alkynylphosphonites (86) with... 

Molecular modelling of 40 complexes derived from ten bicyclic phosphoranes (51-60), and the alkali cations, Li", Na" and has been carried out using the Insight II V97 programme based on the ESFF force field/ Calculations were... 

Reaction of the nitrile-imine 42 with the phosphonite 43 gave the bicyclic phosphorane 46 via intermediates 44 and 45. The structure of 46 was confirmed by elemental analysis, IR, H/ P nmr and finally X-ray crystallography which revealed that the bicyclic structure was almost planar. ... 

Reaction of the hydroxyketone 89 with dichlorophosphines 90a,b gave the unstable phosphonites 9la,b which were trapped in the case of 91a as 92a by hexafluoroacetone. Concerted, thermal decomposition of 91a,b gave 94 and a mixture of diastereomeric phosphinates 95a,b via the intermediate bicyclic phosphoranes 93a,b. ... 

Reactions of Phosphoranes.—Dimethyl(trichloro)phosphorane (94) reacts with 1-acetylsemicarbazides to form the bicyclic phosphoranes (95). . Y-Ray analysis of the bicyclo[3,2,0]heptane derivative reveals a distorted tbp structure for (95). 

From isothiocyanatodialkylphosphites and hexafluoroacetone one btains a 1 1 adduct-bicyclic phosphorane 3 (87AGE921) (Scheme 12). 

Introduction - The year has again seen a consolidation of knowledge in the area of hypervalent phosphorus chemistry with emphasis on the synthesis and properties of monocyclic and bicyclic phosphoranes. A considerable effort has been made to resolve the mechanism of the Mitsunobu Reaction (see Section 3) and the principles established by studies of pentaco-ordinate phosphorus compounds have again been extended to hypervalent compounds of other elements (e.g. As, Sb, and Si). A comprehensive review of the reactions of phosphorus acids with chlorine includes a number of examples of acyclic, monocyclic and bicyclic phosphoranes prepared by this route together with a useful catalogue of their 31p 5-values. 

Phosphoroisocyanatidites (e.g. 83) react with 3-alkylidene-2,4-pentanediones (e.g. 84a) or 2-alkylideneacetoacetic esters (e.g. 84b) to form phosphoranes (85,a,b) which decompose on heating to the cyclic phosphonates (86a, b)27. in an analogous study, dialkylalkynylphosphonates (87) have been shown to react with alkyl pyruvates (88) below 0°C to form mixtures of alkynyl phosphonates (90) and monocyclic tetraoxaphosphoranes (91) via (89)28. At 80°C, however, (89) reacts with excess (88) via (92) to form the bicyclic phosphorane (93). 

In a communication devoted largely to tricoordinate and tetracoordinate benzodiazaphosphorinones, Schmutzler et al. describe the reaction of (68) with hexafluoroacetone to form the bicyclic phosphorane (69) which was characterised by multinuclear NMR and mass spectrometry. Similarly, the reaction of (70a or 70b) with tetrachloro-o-benzoquinone gave (71a) or (71b) respectively but (72) with the same reagent gave the tetracoordinate structure (73). The reaction of... 

An exchange reaction between triethoxydiphenylphosphorane and diethanolamine gave the bicyclic phosphorane (66). 

Reaction of (23) with (24) gave the novel series of bicyclic phosphoranes (25) in 67—69% yield, and a similar displacement of a dialkylamino group from three-co-ordinate phosphorus (26) by the amidoxime (27) gave the phosphorane... 

Bicyclic phosphoranes (87a-d) prepared by the reaction of (85a-d) with (86) were isolated and then characterised by m.s., elemental analysis, i.r. and multinuclear n.m.r. spectroscopy no pseudorotation was observed at ambient temperature. In a related study, tricyclic phosphoranes (89a-d) were obtained from the reaction of (88a-d) with (86). An analogous reaction between (90a-i) and (86) furnished another series of tricyclic phosphoranes (91a-i). The single crystal X-ray structure of (91a) revealed a tbp configuration about phosphorus with a 26% distortion along the Berry coordinate using P-01 as the pivot. 

The reaction of bicyclic phosphoramidites with alcohols offers a simple route to hydridophosphoranes. In particular the oxidative addition of a variety of alcohols (ROH) or phenol (PhOH) with bicyclic phosphoramidites of type (107) give a wide range of bicyclic phosphoranes of type (108) with the P-H bond in an equatorial position. A number of addition reactions with activated double (e.g. fumaric ester) and triple (e.g. acetylene dicarboxylic ester) bonds arc also dcscribcd. The reaction of hydridophosphoranes (109) with alcohols (1 lOa-0 takes a further step in the presence of diphenyl disulphide to generate the alkoxylated products (llla-f). ... 

A Phosphorus System.—Photoelectron spectroscopy of the bicyclic phosphorane (742) reveals that it exists in the open form (743) in the vapour phase the related radical (744), on the other hand, is stabilized with respect to the mono-cyclic valence isomer... 

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