Hydrogenphosphonates with carbonyls

In the many recorded examples of the reaction, and because of its very nature, reports have tended to concentrate on compounds derived from a range of simple carbonyl compounds and a single (or at most two) dialkydiaryP or diheteroaryP hydrogenphosphonate or, alternatively, on combinations of a selection of hydrogenphosphonates with a relatively few carbonyl compounds, including propanal, benzenoid aldehydes " furan and thiophene aldehydes 3-formylindole ° 2- and 3-formyl-chromones " , diethyl oxomalonate and others . It is worthy of comment that... 

In Section VILA, the 1,2-addition of a hydrogenphosphonic diester or related compound to an a,j5-unsaturated aldehyde or analogous ketone " " was discussed in relation to the synthesis of (l-hydroxyalkyl)phosphonic diesters. The latter are formed under condition of kinetic control whereas 1,4-addition (the so-called Pudovik reaction), which leads to the (2-oxoalkyl)phosphonic diester occur under thermodynamic controP" ". In general, reactions which involve ethylenic aldehydes, or acetylenic aldehydes or ketones, tend to result in adduct formation across the carbonyl group, whilst ethylenic ketones tend to take part in 1,4-additions and afford 3-oxoalkyl phosphonic (or phosphinic) acid systems 550 34,946-949 consistent with Markovnikov predictions. Such statements are a broad oversimplification, however, at least with regard to the formation of the oxoalkyl phosphonates. In practice, the manner of addition depends on experimental circumstances, the nature and even amount of catalyst and other factors For instance, for the additions of dimethyl hydrogenphosphonate to the ketones 561 ( = 1 or 2) and 559 (R" = H, R = 2-furyl, R = Me), carried out by the addition of a trace of saturated MeONa-MeOH solution to a mixture of reactants in diethyl ether, yielded (within 5 min) the respective 1,2-adducts (1-hydroxyalkylphosphonates) in yields of64,69 and 52% ... 

The study of the reactions between conjugated unsaturated carbonyl compounds and phosphorus(III) esters has proceeded alongside that of hydrogenphosphonates and related species, generally with the same substrates. 

Carbonyl hydrazones also participate in reactions with hydrogenphosphonate esters, as is illustrated by the formation of the hydrazine derivative 209. The outcome of the reaction between diethyl hydrogenphosphonate and an aromatic aldazine, typically 210, depends on the ratio of reactants. With the reactants in the ratio 1 1, the initial step is the formation of the use of a mixture of the hydrogenphosphonate and sodium... 

A one-pot process has been devised for the synthesis of dialkyl [(a-phenylamino)ben-zyljphosphonates from dialkyl hydrogenphosphonate, benzaldehyde and aniline, presumably adaptable for other aromatic amines or aldehydes To avoid multiple reactions of the Mannich type when using a primary amine and a particularly reactive carbonyl component such as formaldehyde, initial silylation of the amine, or the use of diethyl trimethylsilyl phosphite, are valuable moderating variations The amine can be replaced by a carboxamide" or carbamate ester, conveniently the benzyl ester , and the product can then be selectively deacylated with HBr in acetic acid at room temperature or by hydrogenolysis. Alternatively, even a phosphoric amide may be used to afford an A-phos-phorylated product (221)" ... 

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