Bisphosphonium salts synthesis

By 1989 Mukaiyama had already explored the behaviour of phosphonium salts as Lewis acid catalysts. It was possible to show that the aldol-type reaction of aldehydes or acetals with several nucleophiles and the Michael reaction of a,j3-unsatu-rated ketones or acetals with silyl nucleophiles gave the products in good yields with a phosphonium salt catalyst [116]. In addition, the same group applied bisphosphonium salts as shown in Scheme 45 in the synthesis of ]3-aminoesters [117]. High yields up to 98% were obtained in the reaction of A-benzylideneaniline and the ketene silyl acetal of methyl isobutyrate. Various analogues of the reaction parteers gave similar results. The bisphosphonium salt was found to be superior to Lewis acids like TiCl and SnCl, which are deactivated by the resulting amines. 

And also, conjugated polymers can be prepared through Heck s coupling between dihalide monomer and divinylbenzene monomer. This coupling reaction is very useful when the synthesis of dialdehyde monomer and bissulfonium or bisphosphonium salt monomer is difficult or impossible. But Heck s coupling has a problem in that very often the preparation of divinylbenzene monomers is... 

Dinaphthoazulene 55, having pleiadiene fused with acenaphthalene, was first synthesized by Bestmann and Rupper, as shown in Scheme 4.12 [50]. In this synthesis, reaction of bisylide 56 with l,8-bis(bromomethyl)naphthalene yielded bisphosphonium salt 57, which on alkaUne hydrolysis gave 58 as well as triphenylphosphine oxide. Compound 55 is characterized by the formally fixed double bonds. No alternative Kekule structures that involve these bonds can be drawn without radicals or ions. The fixed double bonds suggest 55 has the nature of a diene more than aromatic azulene although its reactions were not reported. 

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