Substituted benzylphosphonate

However, acidic p-substituted benzylphosphonates as expected fail to offer such correlation (5). 

The reactions of 7-aldiminoalcohol 296 with diethyl and diisopropyl phosphorochloridites in CHCI3 at 0°C afforded diastereomeric mixtures of substituted benzylphosphonates 299 and 300, respectively, which are believed to be formed from a common intermediate, 298 <2005RCB1496>. 

The Horner-Wadsworth-Emmons reaction between bis(benzyloxy)benzalde-hydes and an ester-substituted benzylphosphonate or triethylphosphonoacetate, yield the correponding stilbene or cinnamate derivatives, respectively. These are crucial steps in the synthesis of chiral AB2 monomers which are themselves valuable dendrimer precursors. Standard Horner-Wadsworth-Emmons reactions between P-ketophosphonates and aldehydes have been used in the synthesis... 

Kreutzkamp, N., and Cordes, G., Carbonyl- and cyanophosphonic acid esters. Part 6. a-Substituted benzylphosphonic acid and its derivatives. Arch. Pharm. Ber. Dtsch. Pharm. Ges., 295, 276, 1962. 

At this stage, we made an effort to prepare two enantiomers of open-chain 1-(substituted phenoxyacetoxy)- -(substituted phenyl)methylphosphonates lA, IE and IF series. The herbicidal activity of these optically active substituted benzyl phosphonates lA, IE, and IF were examined. In this section, the synthesis and herbicidal activity of optically active substituted benzylphosphonates lA, IE and IF are introduced. The structure-activity relationships of these optically active compounds together with their racemates are discussed. 

Optically active substituted benzylphosphonates lA, IE and IF could be prepared by the condensation of substituted phenoxyacetyl chlorides MS and optically pure l-hydroxy(substituted phenyl)methylphosphonates M2 (Scheme 6.10). Substituted phenoxyacetyl chlorides MS could be easily synthesized starting from substituted phenols and bromoacetic acid ester [24, 77]. Optically active l-hydroxy(substituted... 

Asymmetric hydrogenation of 1,2-unsaturated phosphonates is a straightforward method for the asymmetric synthesis of some phosphonates [78-80], but this method is not suitable for the synthesis of substituted benzylphosphonates lA, IE, and IF. As stated in Sect. 6.2, three series of optically active 0,0-dialkyl 1-(substituted phenoxyacetoxy)- -(substituted phenyl)methylphosphonates lA, IE, and IF had been successfully prepared by the condensation of substituted phen-oxyacetyl chlorides MS and optically active 1-hydroxy (substimted phenyl)meth-ylphosphonate M2. 

Table 9.43 Structure and physicochemical data of 0,0-diethyl substituted benzylphosphonates M23 ...

The structures, physicochemical data, and yields of (9,0-diethyl substituted benzylphosphonates M23 are listed in Table 9.43. 

In 2014, Lee and coworkers also reported an efficient phosphaannulation by Pd-catalyzed carbonylation of C-H bonds of phosphonic and phosphinic acids for the synthesis of oxaphosphorinanone oxides (Scheme 4.29) [43]. In the reaction, AgOAc and PhI(OAc)2 gave the best result. In the transformation, ethyl hydrogen benzylphosphonate and methyl-substituted phosphonate were totally ineffective. It indicated that introduction of two substituents at the a-position was essential for successful carbonylation. Both electron-donating and electron-withdrawing groups on the aryl ring were tolerated. 

Table 2.9 Structure of 0,0-dimethyl l-(substituted phenoxyacetoxy)benzylphosphonates IE...

Herbicidal Activity of 0,0-Dimethyl 1-(Substituted Phenoxyacetoxy)Benzylphosphonates IE... 

Another approach is stereoselective hydroxylation. The stereoselective hydrox-ylation of dialkyl benzylphosphonates by using chiral reagent could yield enanti-omerically pure l-hydroxy(substituted phenyl)methylphosphonates M2 including M2-6, M2-7, M2-9, and M2-13 (Scheme 6.5) [55, 56]. 

Diethoxy a-hydroxy-benzylphosphonate has been reported to undergo nucleophilic substitution with primary amines to give a-aminophosphonates (Scheme 184) " Primary aromatic amines have been prepared from arylboronic acids in the presence of 0-(2,4-dinitrophenyl)hydroxylamine. " Reaction of iV-t-butanesulfinyl a-haloimines with alkoxides has been reported to give iV-t-butanesulfinyl 2-amino acetals that are precursors for TMSOTf-promoted synthesis of iV-protected a-amino aldehydes and ketones and for the HCl-promoted synthesis of 2-amino acetal hydrochlorides and a-amino ketone and a-amino aldehyde hydrochlorides (Scheme 185). " ... 

Diethyl a-hydroxy-benzylphosphonate (358) underwent nucleophilic substitution with primary amines under solventless MW conditions to afford the corresponding a-aminophosphonates (359) (Scheme 122). 

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