Alkenylphosphonic acids reactions

E. Synthesis of Alkenylphosphonic Acids Using the Wittig Reaction... 

The first successful preparation of phosphorus-containing heterocyclic fatty acid derivatives has been presented. Reaction of cx-keto allene (379) with trimethyl phosphite gave oxaphosphole derivative (380). Similar transformations with a-keto and a-chloro-ot-ketoallenes (381) and (382) led to the formation of alkenylphosphonates (383) and (384), respectively (Figure 64) ... 

The use of esters of a (substituted-methyl)phosphonic acid to provide the carbanion site next to phosphoryl phosphorus was a natural step forward. The most successful development has been the use of the carbanion 346 derived from esters of methylenebisphospho-nic acid (or its monoalkylated derivatives). The anion 346 reacts with an aldehyde to afford the alkenylphosphonic diester 347 (R = Et, Ph, PhCH—CH, 2-thienyl, 2-pyridinyl, etc,) ". Use of the protected 3-pyridinylcarboxaldehyde 348 allowed the preparation of the ester 349, which, after reduction of the C=C bond and hydrolysis, afforded the phosphonic acid 350 Such reactions have also been carried out under phase-transfer condi-tions. Reactions between the lithium salt of the ester 351 and benzaldehyde or but-2-enal give the (alk-1 -enyl)phosphonic esters 352 and 353 in the ratio 1 4 the lithium salts 354 and 355 are formed concomitantly in the ratio 4 1. ... 

Esters and other derivatives of alkenyl- and alkynyl-phosphonic acids, and of the correspondingly unsaturated phosphinic acids, undergo a wide range of addition and cycloaddition reactions which will be considered more fully in Chapter 6. These reactions include applications of the Diels-Alder reaction to yield carbocyclic phosphonic acids based on mono- and poly-cyclic ring systems, some of which are precursors to other aromatic phosphonic acids. A typical example of this procedure is the addition of dimethyl (bromoethynyl)phosphonate to 2,3-dimethylbutadiene elimination of HBr from the 1 1 cycloadduct, using Et3N, affords dimethyl (2,3-dimethylphenyl)phosphonate. The addition of carbenes to alkenylphosphonic derivatives yields those of cyclopropylphos-phonic acids. ... 

The asymmetric conjugate addition reaction has been applied to a,P-unsaturated amides,alkenylphosphonates, and ethenesulfonamides. Hayashi and co-workers have also applied the standard reaction conditions to nitroalkenes. The reaction was found to be applicable to a variety of arylboronic acids. The reaction was also extended to acyclic nitroalkenes without loss of selectivity, but not to nitrocycloheptene or nitrocyclopentene. Interestingly, the thermodynamically less stable cis isomers, e.g., 266, were formed in the reaction of nitrocyclohexene (265) with a wide range of arylboronic acids, e.g., 254. The initial products could be readily converted to the more stable trans isomers by treatment with base. 

Hayashi has reported a wide range of reactions employing rhodium with chiral binaphthylphosphine ligands, for example in the asymmetric 1,4-addition of boronic acids and triarylboranes to various unsaturated starting materials a,p-unsaturated ketones, esters, 1-alkenylphosphonates, nitroalkenes and 5,6-dihydro-2(lH)-pyridinones. ... 

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