P-Aminophosphonium 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. 

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. 

Bertrand et al. have introduced a stable acyclic a-aminophosphonium salt. Only basic phosphines, such as tris(dimethylamino)phosphine, allow for the synthesis of stable aminophosphonium salts. The species mentioned gave upon deprotonation with butyllithium the corresponding C-amino phosphorus ylide (Scheme 100/1). In contrast, two cyclic a-amino phosphonium salts were found to be stable despite the presence of weakly basic triarylphosphine moieties. The key intermediates were dicationic aldiminium salts that on treatment with sodium tert-butylate afforded the cyclic a-aminophosphonium salts under discussion (Scheme 100/2 and 3). In Scheme 100/2, the carbenoid intermediate involved is also shown. On treatment with LiHMDS or BuLi, the stable phosphonium salts were converted to the corresponding P-ylides (Scheme 100/2 and 3). In the second example, the cyclic ylide was transformed to a phosphinoarylenamine derivative via a carbenoid intermediate (Scheme 100/3). ... 

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)... 

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