Reactions from phosphoranes

Vinyl ethers have also been prepared by addition of alkoxides to acetylene,6 7 6 elimination from halo ethers and related precursors,6 8 and vinyl exchange reactions.6 Reaction of an electrophilic tungsten carbenoid with methylene phosphorane or diazomethane also produces vinyl ethers.9 Enol ethers have resulted from the reaction of some tantalum and niobium carbenoids with esters,10 and the reaction of phosphoranes with electrophilic esters.4... 

This variation of the Wittig reaction uses ylides prepared from phosphonates.12 The Horner-Wadsworth-Emmons method has several advantages over the use of phosphoranes. These ylides are more reactive than the corresponding phosphoranes, especially when substituted with an electron withdrawing group. In addition the phosphorus product is a phosphate ester and soluble in water - unlike the Ph3PO product of the Wittig reaction - which makes it easy to separate from the olefin product. Phosphonates are also cheaper than phosphonium salts and can easily be prepared by the Arbuzov reaction from phosphanes and halides. 

Silylated bis(imino)phosphoranes, (Me3Si)2N P(=NSi Mes)2, can be prepared by a Staudinger reaction, from (Me3Si)2N P=NSiMe3 withMesSiNs. ... 

The synthesis of wybutine, wybutosine, and fi-hydroxywybutine employed 4,9-dihydro-4,6-dimethyl-9-oxo-3-[2,3,5-tris-0-(tert-butyldimethylsilyl)-/i-D-ribofurano-syl]-377-imidazo[l, 2-tf]purine-7-carbaldehyde (186), which enabled the introduction of the (a-aminobuten-3-yl(-carboxylic grouping into position 7 of the heterocyclic ring by a Wittig reaction with phosphorane derived from the inner salt of... 

When reviewed in CHEC-I some examples of cyclization y to the heteroatom had been described for the synthesis of pyridazines, but the method was of most importance in the synthesis of cinnolines. Examples of pyridazine syntheses included cyclization of ketazines with EDA, and intramolecular Wittig reactions of phosphoranes derived from phosphacumuleneneylides and the hydrazones produced from 1,3-dicarbonyl compounds and aryldiazonium salts. Synthetically useful approaches to cinnolines given include the intramolecular Friedel-Crafts acylation of the diacid chlorides derived from the condensation products of aryldiazonium salts and diethyl malonate to give 4(l//)-cinnolinones, and thermal cyclization of iminium hydrazones obtained from enamine esters and aryldiazonium salts. 

The first synthesis of 289 and 290 started from the base-catalyzed addition of a sugar containing an isolated hydroxyl group to 2,7-dimethyl-3,5-octa-dyine-2,7-diol (286). Two enynyl ethers (287 and 288) were formed and separated, the partial hydrogenation over a Lindlar catalyst affording dienyl ethers 289 and 290. Alternatively, both ethers were prepared by a Wittig reaction from chloromethyl ether (291) a phosphonium salt (292) was prepared and converted into a phosphorane. Reaction with acrylaldehyde gave a mixture of 289 and 290. 

The reaction of phosphoranes generated in situ from the respective phosphonium salts with the Weinreb amide led to the corresponding aldehyde after acidic... 

The reaction of phosphoranes with alkylmethoxycarbene complexes fails to produce vinyl ethers owing to abstraction of a proton from the carbon alpha to the carbene carbon atom. However, the less basic diazoalkanes react... 

A variety of 1-azirines are available (40-90%) from the thermally induced extrusion (>100 °C) of triphenylphosphine oxide from oxazaphospholines (388) (or their acyclic betaine equivalents), which are accessible through 1,3-dipolar cycloaddition of nitrile oxides (389) to alkylidenephosphoranes (390) (66AG(E)1039). Frequently, the isomeric ketenimines (391) are isolated as by-products. The presence of electron withdrawing functionality in either or both of the addition components can influence the course of the reaction. For example, addition of benzonitrile oxide to the phosphorane ester (390 = C02Et) at... 

Phosphonium hexafluorophosphate, benzotriazolyl-N-hydroxytris(dimethylamino)-in peptide synthesis, 5, 728 Phosphonium salts chromene synthesis from, 3, 753 reactions, 1, 531 Phosphonium salts, vinyl-in pyrrole synthesis, 4, 343 Phosphonium ylides in heterocyclic synthesis, 5, 165 Phosphoramide, triethylene-as pharmaceutical, 1, 157 Phosphoramide, triethylenethio-as pharmaceutical, 1, 157 Phosphorane, pentaphenyl-synthesis, 1, 532 Phosphoranes, 1, 527-537 Berry pseudorotation, 1, 529 bonding, 1, 528... 

The reaction times varied from 10 min to 18 hr. A=the correspondi ng phosphonii salt was used with the addition of two moles of triethyl amine. B=the corresponding phosphorane was used with the addition of one mole of triethylamine. 

The submitters have shown that these reactions proceed by dehydro-chlorination of the acid chloride to the ketene, which is then trapped by reaction with the phosphorane. The resulting betaine decomposes to the allenic ester via an oxaphosphetane. In contrast, the reaction of acid chlorides with 2 equivalents of phosphoranes involves initial acylation of the phosphorane followed by proton elimination from the phosphonium salt. ... 

Bis(tnfluoromethyl -substituted phosphoranes are obtained on reaction of bis(tnfluoromethyl)-substituted heterodienes and P(ni) species [74J, 742 143] In the case of sulfur- and selemum-contaimng phosphoranes, the corresponding heterodienes are generated in situ from heterocyclic precursors [137] (equation 32)... 

In the Wittig reaction an aldehyde or ketone is treated with a phosphorus ylid (also called a phosphorane) to give an alkene. Phosphorus ylids are usually prepared by treatment of a phosphonium salt with a base, and phosphonium salts are usually prepared from the phosphine and an alkyl halide (10-44) ... 

Following a similar protocol, novel hexacoordinated phosphate anions 19 to 22 bearing two different dioxo ligands could be simply prepared as their di-methylammonium salts from the reaction of tetrachlorocatechol derived phos-phoramidite 23 with a variety of symmetrical diones other than o-chloranil (a-diketones or orf/zo-quinones) and subsequent addition of tetrachlorocatechol to the corresponding phosphorane 24 (Scheme 3) [42]. 

Sugars having a difluoromethylene group were prepared by reaction of an aldehyde group in sugars with difluoromethylene tris(dimethyl-amino)phosphorane some of these were 554- 559. Similarly, (Z)- 560) and f ))-. tw-bromofluoroalkene 561 were prepared from l,2 3,4-di-0-iso-propylidene-a-D-gfl/ac/o-hexodialdo-l,5-pyranose (395) by treatment with Ph3P=CFBr. 

In a similar rearrangement dibenzophosphorin oxides (31) have been prepared from the reaction of dibenzophosph(ni)oles with methyl pro-piolate. Some ring expansion occurs even when R = benzyl, presumably because of the difficulty of putting benzyl in an apical position in the intermediate phosphorane. 

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