Phosphinocarboxylic acids

NOTE All-polymer programs employ various types of organic deposit control agents (DCA) such as phosphinocarboxylic acid (PCA) products, which tend to be high temperature-stable sludge dispersants, crystal modifiers, and hardness transporters. 

In general, organic contaminants induce foaming and inorganics increase surface tension, although clearly there are exceptions. For example, sugar increases surface tension, while tannins, lignosulfonates, car-boxymethyl cellulose (CMC), phosphinocarboxylic acids (PCAs), and other dispersants reduce surface tension and help destabilize foams. 

In the meantime improved nickel catalysts have also been developed by workers from Du Pont employing phosphinocarboxylic acids as the ligands... 

Some chelating ligands provide a high to excellent enantioselectivity in the alkylation of cyclic allylic esters. In 1995, Minami and Helmchen independently found some /3-phosphinocarboxylic acids 121 and 122 as effective chiral ligands for the allylic alkylation (Equations (24) d08a (25) ). Helmchen and Kudis also discovered... 

The 1980s produced a wide range of new copolymers, often using chemistry based on acrylic acid with sulfonic acid, sulfonated styrene, or sulfonated acrylamide. Also, new products were introduced based on phosphinocarboxylic acids. All these modern organic polymers found immediate favor as improved iron dispersants, phosphate stabilizers, or corrosion inhibitors, with good thermal and hydrolytic stability. 

These types of polymers are similar to phosphonates and some actually are phosphonates, despite attempts to confuse the issue by the use of alternative names. They tend to exhibit varying degrees of both deposit-control and corrosion-control properties. Several PCA polymers were introduced in the 1980s and further developed in the 1990s and were termed phosphinocarboxylic acids. Most were, in fact, acrylic acid/organic phosphate polymers, but with a C P C bond (the phosphonates have a C P O bond). In the 1990s some low phosphorus content phosphonocarboxylic acid PCAs have been introduced. Structures for the different chemical PCAs, types 16 and 4, are shown in Figure 5.5. 

Low phosphorus content, Cl resistant, ferrous corrosion inhibitor PCA (Type 16) Phosphinocarboxylic acid (phosphino/acrylic acid polymer)... 

Other chiral ligands to highlight include those prepared by Trost (e.g., (166)),376 chiral /3-phosphinocarboxylic acids (167),377 the aminodiphosphine (168),378 and the poly(tertiary) phosphines (169)379 and (170) (Scheme ll).380 Although far from exhaustive, this section summarizes just some of the chiral ligands reported to date. 

Belcor 575. [Ciba-Geigy] Hydroxy phosphinocarboxylic acid corrosion inhibitor for ferrous metals. 

Beisperse. [Ciba-Geigy] Phosphinocarboxylic acid dispersant for industrial water systems. 

Lithiated 71 (Ar = o-An, u-Tol and 1-Naphth) reacted with carbon dioxide affording the phosphinocarboxylic acid boranes 74 in 55-60% yields. Their deprotection using TFA, with retention of conflguration, and coupling with (S)-(—)-2-(diphenylphosphino)methylpyrrolidine furnished amidodiphosphines 81 (48-51% yield). Finally, carbonyl reduction with borane (and concomitant N-and P-protection) followed by a deboronation step gave access to P,N ligands 82. 

Scheme 4.35 Preparation of P-stereogenic phosphinocarboxylic acids, amido- and aminodiphosphines.

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