Phosphinic acids, unsymmetrically substituted

Unsymmetrically substituted phospha-methin-cyanines 9 with two different heterocyclic bases can also be synthesized. Here the quaternary salt of one heterocyclic base (e. g. 4) is reacted with tris-hydroxymethyl-phosphine 5 in dimethyl-formamide or glacial acetic acid without the addition of a base. Then one mole of the quaternary salt of the other heterocyclic base (e. g. 10) and the base are added. The base deprotonates the hydroxymethyl groups of the phosphine 5, thus liberating formaldehyde and yielding the phosphine base which then reacts with the second quaternary salt ... 

In the simplest form of the Abramov reaction, the phosphorus-containing reactant is hypophosphorous acid (phosphinic acid) or an ester thereof, and in the reactions between the acid and formaldehyde or benzaldehyde the initial product is the phosphinic acid 144 (R = H or Ph.). However, the reaction can proceed further to give the bis(l-hydroxyalkyl)phosphinic acid (145 R = H or Ph) the latter (R = Ph) reacts readily with yet more benzaldehyde to give its benzylidene derivative, 5-hydroxy-2,4,6-triphenyl-1,3,5-dioxaphosphorinane 5-oxide (146 R = Ph). When acted on by a second mole of cyclohexanone in the presence of acetyl chloride, (l-hydroxycyclohexyl)phosphinic acid (147) gives the novel phosphinic chloride 148, characterized as the free acid 149 following ready hydrolysis A reaction between a phosphinic acid (150) and a second (non-identical) carbonyl compound leads to an unsymmetrical phosphinic acid (151). Esters of symmetrical 1, r-dihydroxy-substituted phosphinic acids are preparable from hypophosphite esters, H2P(0)0R ". ... 

In the presence of Lewis acids such as EtsAl, EtaAlCl, and BF3 OEt2, the silylphosphine reacted with aldehydes and epoxides to give the corresponding a- and /3-hydroxyalkylphosphine derivatives, respectively (eqs 6 and 7)5 The more substituted alkylphosphine was preferentially formed by using an unsymmetrical epoxide. This is in contrast to the basic phosphination of epoxides, which provides mainly less substituted alkylphosphines. ... 

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