Phosphinic imidazolides

Fluorophosphates (phosphorfluoridates), which are important for backbone modified oligonucleotides in molecular biology, are generally synthesized from phosphoric imi-dazolides or triazolides and acylfluorides. In these reactions, for example, the azole group (of the phosphoric or phosphinic imidazolide) is substituted by a fluorine atom, forming an acylazole compound as by-product.[202],[2033... 

A-Phosphorylated imidazoles and benzimidazoles can be made by direct phosphorylation by halides, esters, amides, amidoesters, isocyanates, and thiocyanates of phosphorus-containing acids, or from reaction of phosphonic or phosphinic imidazolides with a sulfonic acid or anhydride <82CB1636>. Stable charge transfer complexes are produced when a 1 1 or 1 2 ratio of imidazole (or benzimidazole) and sulfur trioxide are refluxed in ether, dioxane, THE, or 1,2-dichloroethane. These complexes are stable on storage in the absence of water and have sharp melting points. Indeed, the benzimidazole SO3 complex must be boiled for five hours in water to decompose it. On fusion, the complexes form the C-sulfonic acids (see Section 3.02.5.3.3) <87CHE1084>. Sulfonyl chlorides readily A-sulfonate imidazoles <94JMC332>. 

The reaction of interest occurs when either the imidazolide or the alcohol is initially bound in the form of a Pt(II) olefin or phosphine complex. 1461... 

Analogously to the phosphorylation of alcohols with phosphoric azolides the phos-phinylation is carried out by means of phosphinic azolides (CH2CI2/C2H5OC2H5). In the following case a I2/C2H5OC2H5) protonated diphenylphosphinic imidazolide is used to give the allylic diphenylphosphinic esters in good yields ... 

Method A permitted the synthesis of an optically active phosphinic-sulfonic anhydride via the optically active imidazolide 2051... 

Imidazolesulfonic acid reacts with phosphinic and phosphoric imidazolides to give mixed anhydrides of the following type 1501... 

With the phosphoric imidazolides D, E, and F, dehydration of the aldoximes can also be achieved (dioxane, room temperature, several hours). With diphenylimidazole-1-phosphonate (D) and phenyldiimidazole-l,l -phosphinate (E) the yields of nitriles are always higher than with (C6H50)2P(0)C1 and C6H50P(0)C12 however, with phosphoryl triimidazole (F) the yields are a little lower than with POCl3.[9] Spin-labeled phosphoric imidazolides of this type are also used for the dehydration of aldoximes.1103... 

Earlier, reference was made to the potential third mechanism associated with nucleophilic displacements at phosphoryl phosphorus, namely that which might involve the participation of a phosphaacylium cation. Mixed sulphonic-phosphonic or sulphonic-phosphinic anhydrides 645 (Z = O, R = Me or 4-methylphenyl) have been obtained from the free phosphorus(V) acid and the 1,2,4-triazole 646 in the presence of trifluoromethanesulphonic acid, or 645 (Z = O, R = CF3) from the imidazolides 647 and trifluoromethanesulphonic acid and / r/-butylphenylphosphinothioic acid with trifluoromethanesulphonic anhydride yield the mixed 0-anhydride 648 (R = CF3), some reactions of which are illustrated in Scheme 76 ". Of those reactions, the formation of the iodide 649, albeit in low yield when the reaction is carried out in MeOH, with stereochemical retention of configuration at phosphorus, contrasts with the inversion of configuration observed for the remainder, and which is normally encountered for Sn2(P) displacements. The reaction of648 with methoxybenzene to yield the phosphine sulphide 650 in a solvent of high ionizing power (1,1,1,3,3,3-hexafluoropropan-2-ol a lower yield was obtained in a... 

CeH,),P [(CH,),NkP l(CH,m,PO Phosphinic acid amides Phenyl phosphorodi-(1-imidazolidate) Phosphazo compounds Trichlorophosphazo-sulfonyl compounds Phenylphosphonic dichloride (C,H,),PO... 

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