Aminophosphonium

The mixed lithium aminophosphonium azadiylides 7 [47] are known to be involved in reaction with various electrophiles specifically at the carbon center. The reaction with carbonyl known to form betaine adducts was recently used for the first time in Wittig type reactions for the synthesis of di-, tri-, and tetrasubsti-tuted alkenes 8 [52]. 

Tetrasubstituted phosphinous amides of the type R2NPPh2 have been successfully arylated at phosphorus by the action of bromobenzene, in a process catalyzed by NiBr2, to give the aminophosphonium bromides [R2NPPh3] Br [109]. Other representative members of this class form phosphane-borane complexes [62], are aminated at phosphorus by chloramine to yield bis(amino)phos-phonium salts [110] and have been claimed to be protonated at phosphorus by ethereal tetrafluoroboric acid, as determined by NMR analysis [111]. 

The simultaneous addition of ammonia or amines and carbon tetrachloride to phosphines yields aminophosphonium chlorides (45). 

When an aminophosphonium species is used with an aryl lithium reagent, cleavage of the amino functionality from phosphorus is observed, producing the parent phosphine.10 This reaction has been used to prepare stable phosphoranes from aminophosphonium species using dilithium reagents (Figure 5.6).10 It should be noted that the... 

Figure 5.6 Formation of a phosphorane from an aminophosphonium salt.

Miscellaneous. The reaction of the aminophosphonium salt (156) with thiols and alkoxides affords a convenient, high-yield, single-step synthesis of unsymmetrical thioethers.141 The key intermediate is the alkoxyphosphonium salt (157), which undergoes nucleophilic attack by RS- at the alkoxy carbon. 

The synthesis of phosphazenes starting from aminophosphonium salts appears to be conveniently accomplished by the reaction of the phosphonium azide with sodamide in liquid ammonia solution 49... 

Whereas the reactions of chloramines of the type R2NCI (where R = H or an alkyl group) with tertiary phosphines have been abundantly investigated and almost without exception lead to the formation of aminophosphonium chlorides or their condensation products Highsmith and Sisler... 

TABLE 2. 31P NMR chemical shifts (ppm) of phosphonium and aminophosphonium halides35,37 (also steric compression was shown to give upfield 31P chemical shifts in cycloalkyltriphenylphosphonium salts)... 

A notable deshielding jS-effect (10 ppm) has been observed in an aminophosphonium salt on the P+NMe 13C chemical shift when the NHMe group is further alkylated to NMe237. Steric compression has been used, with some caution, to explain the relatively shielded / -carbon atoms in triphenylphosphonio cycloalkyl salts when they are compared with their methylcycloalkyl analogues36. 

Finally, heterophosphonium salts are reduced with cleavage of the phosphorus-heteroatom bond optically active aminophosphonium compounds are usefully reduced to phosphines with retention of configuration747. Methyltrineopentoxyphosphonium trifluoromethanesulphonate gave the quantitative formation of dineopentylmethyl phos-phonite, which is indicative of P—O bond cleavage748 (reaction 223)... 

A more concise route to ( )-cherylline was also devised and commenced with the reductive animation of isovanillin with methylamine followed by reaction of the intermediate benzylamine with vinyl triphenylphosphonium bromide to provide the aminophosphonium salt 619. Sequential treatment of 619 with n-butyllithium and the quinone ketal 615 followed by reaction of the resulting crude allylic amine 620 with boron trifluoride etherate gave the phenolic amine 618 in good overall yield (225). 

Aminophosphane addieren sich an aktivierte Alkene, wie Acrylsaure-Derivate Michael-artigzu Aminophosphonium-betainen, die sich durch Umprotonierung zu tert.Phosphan-imiden stabilisieren6 4 z.B. ... 

Diese Methode ist bereits in Bd. XII/1, S. 175, beschrieben, hat aber in neuerer Zeit durch Verbesserung der Aminophosphonium-Salzsynthesen an Bedeutung gewonnen. 

Auch die Aminophosphonium-Salze, die aus tert. Phosphanen und dem System Tetra-chlormethan/Amin672,6728 gebildet werden (s. Bd. El, S. 534), konnen mit Basen deprotoniert bzw. als Zwischenstufen direkt zu tert.-Phosphanen umgesetzt werden. 

Uber Aminophosphonium-Salze sind auch Phosphazine zuganglich (s. Bd. XII/1, S. 181). Hydrazino-phosphonium-Salze setzen sich in guten Ausbeuten mit Aldehyden oder Keto-nen zu Phosphazinen urn699 ... 

Tab. 14 tert.-Pbosphanimide aus oder liber Aminophosphonium-Salze... 

Die Phosphanimide werden nieht in Substanz isoliert, sondern als Aminophosphonium-Salze charakterisiert. Eingesetzt werden prim. Lithiumamide wobei man z.B. Triphenyl-phosphan-methylimid, -ethylimid, -butylimid (70—93%) erhalt. 

Aminophosphonium-Salze mit einer P—N—P-Kette entstehen beider Umsetzung von Phosphan-silylimiden mit Halogenphosphanen740-743 oder Halogenphosphoranen744-745 (s. Bd. El, S. 536) z.B. ... 

A less commonly employed method of preparation is the Kirsanov reaction.3 Strictly speaking, this is the reaction of phosphorus pentachloride with benzene-sulfonamide, which can be reacted further to form benzenesulfonyliminophos-phoranes. However, the name is now used generically to cover the reactions of triphenylphosphorus dihalides and amines in the presence of a base (Scheme 5). Attack of the amine on phosphorus gives the intermediate aminophosphonium salt and HBr, elimination of another equivalent of HBr generates the IMP. If the amine is aromatic, then 2 eq. of a mild base (e.g. triethylamine) are sufficient to perform the reaction in one pot.4 However, in the case of alkylamines, it is generally necessary to isolate the phosphonium salt and treat it with sodamide to effect the deprotonation and generate the IMP.5... 

For less activated aromatic systems (those without a nitro substituent), the halogcn-ex-changc reaction has been investigated with potassium fluoride in a variety of polar aprotic solvents in the presence or absence of a catalyst (see Table 13). Many different types of catalysts have been investigated these include crown ethers, quaternary ammonium salts, 3,164 pjjos-phonium salts, aminophosphonium salts, compounds containing a phosphorus and an amino function, and inorganic fluorides of boron, aluminum, tin, phosphorus, titanium and zirconium. Different forms of potassium fluoride have been used these include spray-dried potassium fluoride, freeze-dried potassium fluoride, potassium fluoride recryslal-lized from methanol, and potassium fluoride dispersed on caleium fluoride. ... 

With alkylamines, the primary reaction products are aminophosphonium salts, [Ph3PNHR]+Br , which need to be dehydrobrominated with ammonia or sodium amide. In a similar marmer, dichlorotriphenylphosphorane reacts with hydrazine dihydrochloride, at 180-220 °C, to form a bis(phosphorane)diimine after treatment with a strong base (hquid ammonia or potassium teri-butoxide), equation (3). ... 

Aminophenyl ketones 43 reaet with triphenylphosphorane dithioeyanatc in diehloromethane solution to give the aminophosphonium salts 44 as intermediates which undergo spontaneous cyclocondensation to 4-substitiited quinazoline-2(l//)-thiones 45. ... 

Tertiary amines. Transformation of alcohols ROH to tertiary amines RR R"N is readily achieved on reaction of the derived sodium alkoxides with (R R"NPPhj)I. The aminophosphonium salts can be obtained by an exchange reaction between (PhN[Me]-PPhj)I and excess R R"NH. 

Preparation. Sisler and co-workers developed a technique for obtaining chloramine by gas-phase reaction of chlorine with excess ammonia and showed that the reagent combines with tertiary amines to form the corresponding 1,1,1-trisubstituted hydrazinium chlorides (1) in good yield, and with tertiary phosphines to form aminophosphonium chlorides (2). The product of reaction (2) can be dehydrohalo-genated with magnesium hydride to triphenylphosphine amine. 

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