Hydrophosphonylations palladium

Scheme 5-18 Stoichiometric reactions relevant to the proposed mechanism for palladium-catalyzed hydrophosphonylation of alkynes...

A bimetallic catalyst prepared from BINOL and lithium aluminum hydride has been found to result in useful asymmetric induction in the Pudovik reaction [17]. The (f )-ALB catalyst 64 (10 mol %) facilitates the addition of dimethyl phosphite to a variety of electron-rich and electron-poor aryl aldehydes in high yield with induction in the range 71-90 % ee. The nature of the solvent is important in this reaction—the induction for addition to benzaldehyde dropped from 85 % ee to 65 % ee when the solvent was changed from toluene to dichloromethane. Aluminum seems to be a key to the success of this reaction, because reaction with benzaldehyde was not as successful with other bimetallic catalysts. BINOL catalysts with lanthanum and potassium gave only 2 % ee, a catalyst with lanthanum and sodium gave a low 32 % ee, and a catalyst with lanthanum and lithium gave only a 28 % ee [18]. Aliphatic aldehydes were not successfully hydrophosphonylated with dimethyl phosphite by catalyst 64 (Sch. 9). Induction was low (3-24 % ee) for unbranched and branched substrates. a,/3-Unsaturated aldehydes were, however, reported to work nearly as well as aryl aldehydes with four examples in the range 55-89 % ee. The failure of aliphatic aldehydes with this catalyst can be overcome by reduction of the product obtained from reactions with a,)3-unsaturated aldehydes. As illustrated by the reduction of 67 with palladium on carbon, this can be done without epimerization of the a-hydroxy phos-phonate. 

The synthesis of phosphorus-containing heterocycles has been reported using a palladium-catalyzed approach (Scheme 4.172) [261]. The overall process involved two phosphorus-carbon(sp ) bond-forming reactions and started with a hydrophosphonylation reaction using a supported palladium catalyst to promote the addition. Conversion of the... 

The palladium-catalysed hydrophosphonylation of alkenes (320) with acyclic diall l phosphites (i -phosphonates) afforded the corresponding phosphonates (321) in moderate to good yields and with excellent levels of regioselectivity (up to >1 99 ot/p) (Scheme 88)/ °... 

Metal-catalyzed hydrophosphonylation of C=C emerged in the 1990s as an efficient method for the formation of C(5p )—P bonds.Palladium, rhodium, and nickel catalysts are most commonly used, and the choice of the metal and ligands influences the... 

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