Aminophosphonium salts

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... 

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. 

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). 

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. 

Cyclic aza-ylides can be generated from the cyclic aminophosphonium salts... 

The reactions of phosphazenes (prepared in situ from aminophosphonium salts and triethylamine) with sulphur tetrafluoride have been further explored. An example is shown in reaction (3), where X is a bridging alkyl or aryl group. However, when X... 

Predictably, aminophosphonium salts are the products of the reaction of aminophosphines with chloramines. ... 

Unsymmetrical sulfides. Unsymmetrical sulfides can be prepared in 65-85% yield by reaction of sulfides with the sodium salts of alcohols in the presence of this aminophosphonium salt (equation I). The sulfuration proceeds with inversion of configuration (equation II). 

Aminophosphines, phosphinites and phosphonites from quasi-phosphonium salts with alkyl halides in normal 5 n reactions. The aminophosphonium salts and the salts derived from aryl phosphinites and diaryl phosphonites are stable, but the majority of the quasi-phosphonium salts which contain alkoxy groups are dealkylated during the reaction with the alkyl halide (the Arbuzov reaction, see below). Thio analogues of phosphinites and... 

The apparatus used for the generation of chloramide is the same as described previously d The gaseous effluent of the chloramide generator (at a flow rate of ca. 0.1 mol of chloramide per hour) is passed into a solution of 5.0 g. (0.19 mol) of triphenylphosphine in 35 ml. of dry benzene maintained at 15 to 25°. Crystallization of (triphenyl)-aminophosphonium chloride begins to occur as the chloramide is passed through the solution. The reaction is continued for 10 to 15 minutes. The reaction mixture is filtered and the residue washed thoroughly with ethyl ether and dried. The washed residue (4.8 to 5.2 g.) consists of (triphenyl) aminophosphonium chloride contaminated with 2 to 4% of ammonium chloride. The yield of aminophosphonium salt is better than 95%. The product, which melts at 224 to 227°, is sufficiently pure for most synthetic work. 

Boiling a solution of (2,2-dimethylhydrazino) diphenyl-phosphine in benzene overnight in contact with dry air causes precipitation of the oxide, (CeH ) P(0)NHN(CH3) (m.p. 167 to 168°). Addition of a stoichiometric amoimt of sulfur to a boiling benzene solution of (2,2-dimethylhydra-zino)diphenylphosphine yields, on cooling, the sulfide, (C6H6)2P(S)NHN(CH8)2 (m.p. 95.5 to 97.0°). Alkylation to [(C6H5)2(CH3)PNHN(CH3)2]I (m.p. 156 to 158°) occurs upon reaction with methyl iodide in ether. Reaction with chloramine in ether yields the aminophosphonium salt, [(C H3)jP(NH2)NHN(CH,)2]C1 (m.p. 195°). All of the above-described derivatives are colorless solids. 

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