Double bonds phosphorus nucleophile addition

Addition of Phosphorus Nucleophiles to C=C Bonds Phosphorus nucleophiles, both neutral and anionic, undergo addition to activated carbon—carbon double bonds. Such reactions constitute a phosphorus analogous of the conjugate addition, and they are often referred to as phospha-Michael addition. For hydrophosphonylation of inactivated double bonds, radical conditions are a viable option. In the last 15 years, however, an attractive alternative of a transition-metal-catalyzed hydrophosphonylation has also emerged. ... 

The initial step of olefin formation is a nucleophilic addition of the negatively polarized ylide carbon center (see the resonance structure 1 above) to the carbonyl carbon center of an aldehyde or ketone. A betain 8 is thus formed, which can cyclize to give the oxaphosphetane 9 as an intermediate. The latter decomposes to yield a trisubstituted phosphine oxide 4—e.g. triphenylphosphine oxide (with R = Ph) and an alkene 3. The driving force for that reaction is the formation of the strong double bond between phosphorus and oxygen ... 

CHMe, cyclopropylidene, and CMe2 to activated double bonds.1075 Similar reactions have been performed with phosphorus ylides, 076 with pyridinium ylides,1077 and with the compounds (PhS)3CLi and Me3Si(PhS)2CLi.1078 The reactions with ylides are of course nucleophilic addition. 

The most common method for the synthesis of phosphinopeptides is the addition of a nucleophilic, trivalent phosphorus species to a carbon electrophile, including conjugated double bonds, alkylating agents, imines, and carbonyl compounds. By analogy with the phosphite ester additions described above, the nucleophilic form of a phosphinic acid is the trivalent species, generated from the more stable, pentavalent PH derivative by deprotonation or by silylation (cf. Scheme 2). 

Previous reactions in this chapter have involved only addition of the nucleophile and a hydrogen to the carbonyl group. In this reaction, addition is followed by elimination of the oxygen to form a double bond between the carbonyl carbon and the nucleophile. Such an addition-elimination reaction occurs when the nucleophile has or can generate (by the loss of a proton or a phosphorus group) a second pair of electrons that can be used to form a second bond to the electrophilic carbon. In the case of the Wittig reaction, the phosphorus and the oxygen are eliminated to form the alkene. The forma-... 

As shown in Fig. 8, two possibilities are conceivable for the addition step of the imine to the lanthanoid-phosphite complex Ha. To determine whether structure V or VI seems to be the more reasonable in the addition reaction of a dimethyl phosphite with the C=N double bond of cyclic imines, several hydrophos-phonylation experiments using different types of phosphites were carried out in the presence or absence of the Lewis acid boron trifluoride. As it was shown that a high level of Lewis acid activation of the imine is required independently from the nucleophilicity of the phosphorus nucleophile which was used, a transition state of type VI appeared to exist as the dominant transition state structure. 

The addition of the phthalimido anion to triesters of 2-phosphonopropenoic acid at room temperature gives an initial adduct, which is unexpectedly inert to benzaldehyde reaction but which adds to a second molecule of the phosphonic diester to form a second carbanion the latter undergoes an intramolecular WEH condensation to give the heterocyclic system 371 indolizine and quinolizine phosphonic diesters have been similarly obtained from maleimide, succinimide and glutarimide anions ". The ability of piperidine to add to the compounds 372 decreases in the order R R = (BuO)H (exothermic reaction) > (BuO)2 > (BuO)Me > Bu2 (the last requires heat) ". Ethenylphosphonic diamides (372 R = r2 = NR2) are unreactive to nucleophiles (by virtue of reduced electrophilic character at phosphorus and thus reduced electron attraction from the carbon-carbon double bond) but are reactive to electrophilic reagents. ... 

Carbon-carbon double bonds, whether attached directly to or are distant from the phosphorus, can undergo some unusual reactions, particularly when treated with electrophilic reagents such as the halogens or pseudo-halogens, a behaviour attributable to phosphoryl nucleophilic character. Ethenylphosphonic acid and its simple derivatives add chlorine or bromine with the expected overall results, but the normal addition of the latter is rapidly accelerated by UV radiation and inhibited by added iodine, suggestive of a homolytic nature Dialkyl (pent-4-enyl)phosphonates (373 R = RO, X = CH2, n = 2) equally add bromine to give the expected dibromo adducts, but their behaviour towards iodine is more complex (Scheme 49). In reactions in CHCI3 at ambient temperature, not only are the expected 4,5-diiodo adducts 374 formed, but so is an additional species, probably a quasi-... 

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